,,on ,,laboratory ,,arts ,,by ,,ri*>d ,,?relfall1 ,m4,a4 ,,pr(essor ,,( ,,physics ,,9 ,,! ,,univ]sity ,,( ,,sydney2 ,,memb] ,,( ,,! ,,in/itute ,,( ,,electrical ,,eng9e]s2 ,,associate-,,memb] ,,( ,,! ,,in/itute ,,( ,,civil ,,eng9e]s2 ,,memb] ,,( ,,! ,,physical ,,society ,london ,,macmillan ,,& ,,co1 ,,limit$ ,,new ,,york3 ,,! ,,macmillan ,,company #ahih ,all rights res]v$ ,,preface #e ,,*apt] ,i #h ,,h9ts ,,on ,,! ,,manipulation ,,( ,,glass ,,& ,,on ,,glass-,,bl[+ ,,= ,,laboratory ,,purposes #h #d4 ,s(t ,soda ,glass4 #f4 ,fl9t ,glass4 #i4 ,h>d or ,bohemian1 ,glass4 #aj4 ,on ! ,*oice ( ,sizes ( ,glass ,tube4 #aa4 ,te/+ ,glass4 #ac4 ,clean+ ,glass ,tubes4 #ad4 ,! ,bl[-pipe4 #ah4 ,! ,table4 #ai4 ,special ,op]ations4 #bj4 ,clos+ & bl[+ out ! ,end ( a ,tube4 #ba4 ,to make a ,weld4 #bb4 ,to weld two ,tubes ( diff]5t ,sizes4 #bd4 ,to weld ,tubes ( v small ,bore4 #cj4 ,to cut v ?ick ,tubes4 #ca4 ,to bl[ a ,bulb at ! ,end ( a ,tube4 #cb4 ,to bl[ a bulb 9 ! middle ( a tube4 #cc4 ,to make a side ,weld4 #cd4 ,ins]t$ ,jo9ts4 #ce4 ,b5d+ ,tubes4 #cf4 ,spiral ,tubes4 #cg4 ,on ,auxili>y ,op]ations on ,glass4 #ch4 ,bor+ small ,holes4 #ci4 ,= bor+ l>ge holes ?r\gh ?ick glass %eets4 #da4 ,op]ations dep5d+ on ,gr9d+3 ,gr\nd-9 ,jo9ts4 #db4 ,use ( ! ,la! 9 ,glass-work+4 #df4 ,mak+ ,gr\nd ,glass4 #dg4 ,glass-cutt+4 #dh4 ,cem5t+4 #di4 ,fus+ ,electrodes into ,glass4 #ea4 ,! ,art ( mak+ ,air-light ,jo9ts4 ,,app5dix ,,to ,,*apt] ,i4 ,,on ,,! ,,prep>ation ,,( ,,vacuum ,,tubes ,,= ,,! ,,production ,,( ,,pr(essor ,,ro5tg5',s ,,radiation4 ,,*apt] ,,ii4 ,,glass-,,gr9d+ ,,& ,,opticians' ,,"w4 #fa4 ,details ( ! ,process ( ,f9e ,gr9d+4 #fb4 ,poli%+4 #fc4 ,c5t]+4 #fe4 ,prep>+ ,small ,mirrors = ,galvanomet]s4 #ff4 ,prep>ation ( ,l>ge ,mirrors or ,l5ses = ,telescopes4 #fi4 ,! ,prep>ation ( ,flat ,surfaces ( ,rock ,salt4 #gj4 ,ca/+ ,specula = ,mirrors4 #ga4 ,gr9d+ & poli%+ ,specula4 #gb4 ,prep>ation ( ,flat ,surfaces4 #gc4 ,poli%+ ,flat ,surfaces on ,glass or on ,speculum ,metal4 ,,*apt] ,,iii4 ,,miscellane\s ,,processes4 #gd4 ,coat+ ,glass ) ,alum9ium & ,sold]+ ,alum9ium4 #ge4 ,! ,use ( ! ,diamond-cutt+ ,:eel4 #gf4 ,arm+ a ,:eel4 #gg4 ,cutt+ a ,section4 #gh4 ,gr9d+ ,rock ,sections1 or ,?9 ,slips ( any ,h>d ,mat]ial4 #gi4 ,cutt+ ,sections ( ,s(t ,sub/ances4 #hj4 ,on ! ,production ( ,qu>tz ,?reads4 #hd4 ,draw+ ,qu>tz ,?reads4 #hf4 ,draw+ ,?reads by ! ,catapult4 #hg4 ,draw+ ,?reads by ! ,flame alone4 #hh4 ,prop]ties ( ,?reads4 #ij4 ,on ! ,atta*m5t ( ,qu>tz ,fibres4 #ia4 ,o!r ,modes ( sold]+ ,qu>tz4 #ib4 ,sold]+4 #id4 ,prep>+ a ,sold]+ ,bit4 #ie4 ,s(t ,sold]+4 #ig4 ,sold]+ ,z9c4 #ih4 ,sold]+ o!r ,metals4 #ii4 ,braz+4 #ajj4 ,silv] ,sold]+4 #aja4 ,on ! ,con/ruction ( ,electrical ,app>atus--,insulators4 #ajb4 ,sulphur4 #ajc4 ,fus$ ,qu>tz4 #ajd4 ,glass4 #aje4 ,ebonite or ,h>d ,rubb]4 #ajf4 ,mica4 #ajg4 ,use ( ,mica 9 ,cond5s]s4 #ajh4 ,micanite4 #aji4 ,celluloid4 #aaj4 ,pap]4 #aaa4 ,p>aff9$ ,pap]4 #aab4 ,p>aff94 #aac4 ,vasel9e1 ,vasel9e ,oil1 & ,k]os5e ,oil4 #aad4 ,imp]fect ,conductors4 #aaf4 ,conductors4 #aag4 ,plat9oid4 #aai4 ,plat9um ,silv]4 #abj4 ,plat9um ,iridium4 #aba4 ,mangan94 #abb4 ,o!r ,alloys4 #abc4 ,nickel94 #abd4 ,pat5t ,nickel4 #abe4 ,con/ant94 #abf4 ,nickel ,manganese ,copp]4 ,,*apt] ,,iv4 ,,electroplat+ ,,& ,,alli$ ,,arts4 #abg4 ,electroplat+4 #abh4 ,! ,dipp+ ,ba?4 #acj4 ,scrat*-bru%+4 #aca4 ,burni%+4 #acb4 ,silv]-plat+4 #acc4 ,cold ,silv]+4 #acd4 ,gild+4 #ace4 ,prep>+ ,surfaces = ,gild+4 #acf4 ,gild+ ,solutions4 #acg4 ,plat+ ) ,copp]4 #ach4 ,copp]+ ,alum9ium4 #adj4 ,alkal9e ,copp]+ ,solution4 #ada4 ,nickel-plat+4 #adb4 ,miscellane\s ,notes on ,electroplat+4 #adc4 ,black+ ,brass ,surfaces4 #add4 ,sieves4 #ade4 ,pott]y mak+ 9 ! ,laboratory4 ,,app5dix4 ,,plat9is+ ,,glass4 ,,preface ,,exp]im5tal "w 9 physical sci5ce re/s ultimately ^u ! me*anical arts4 ,x is true t 9 a well-appo9t$ laboratory1 :]e app>atus is collect$ toge!r 9 great] or less pr(usion1 ! appeal is (t5 v indirect1 & to a /ud5t c>ry+ out a set exp]im5t ) app>atus provid$ to 8 h&1 ! temptation to ignore ! me*anical basis ( 8 "w is (t5 irresi/ible4 ,x (t5 happ5s t "y physici/s are to be f\nd ^: ma!matical atta9m5ts are adequate1 ^: obs]vational p[]s are p]fectly tra9$1 & ^: g5]al capacity is unque/ion$1 b :o are q unable to design or con/ruct ! simple/ app>atus ) due reg>d to ! facility ) :i* x ought to be con/ruct$4 ,t ultimate k ( mat]ials & ( processes :i* by long exp]i5ce becomes intuitive 9 ! m9d ( a great inv5tor ( c\rse _c be acquir$ f books or f any set c\rse ( in/ruction4 ,!re are1 h[ev]1 _m /eps betwe5 absolute ignorance & consummate k ( ! me*anical arts1 & x is ! object ( ! foll[+ pages to assi/ ! "y physici/ 9 mak+ 8 fir/ /eps t[>ds acquir+ a work+ k ( laboratory arts4 ,h[ev] humble ! ambition may be1 no "o c be m ke5ly alive ?an ! writ] to ! inadequacy ( 8 attempt2 & x is only f a pr(\nd s5se ( ! necessity :i* exi/s = "s beg9n+ to be made1 t he has _h ! c\rage to air 8 views on matt]s ab\t :i* !re are probably hundr$s or ?\s&s ( p ^: k is sup]ior to 8 own4 ,moreov]1 no?+ has be5 fur!r f ! writ]'s m9d ?an any idea ( in/ruct+ any "o2 8 desire is--if happily x may s befall--to be ( assi/ance1 especially to "y physici/s or inv5tors :o wi% to atta9 def9ite me*anical ends ) ! m9imum exp5diture ( "t4 ,mo/ p w agree t "o condition ess5tial to success 9 su* an und]tak+ is brevity1 & x is = ?is reason t alt]native me?ods z a rule h n be5 giv51 :i*1 ( c\rse1 deprives ! book ( any pret5ce to be+ a treatise4 ,! writ]1 !re=e1 is responsible = ex]cis+ a c]ta9 am\nt ( discretion 9 ! selection he has made1 & x is h>dly to be hop$ t he has 9 all--or ev5 9 ! majority ( cases--succe$$ 9 recomm5d+ absolutely ! be/ me?od ( proc$ure4 ,?is br+s ano!r po9t into view4 ,be=e all ?+s ! means indicat$ mu/ be def9ite & reliable4 ,x is = ?is reason t ! writ] has practically conf9$ himself to matt]s ly+ )9 8 own imm$iate exp]i5ce1 & has nev] recomm5d$ any process 7) "o or two m9or exceptions1 :i* he has not$7 :i* he has n actually & p]sonally c>ri$ ?r\gh to a successful issue4 ,?is1 al?\gh x is a matt] :i* he consid]s ( ! highe/ importance1 & :i* is 8 only title to a he>+1 has un=tunately l$ to a v p]sonal tone 9 ! book4 ,) reg>d to ! arts treat$ ( 9 ! foll[+ pages1 matt]s ab\t :i* in=mation is easily acquir$--su* z c>p5t]+1 blacksmi?+1 turn+1 & ! arts ( ! wat*mak]--h be5 left on "o side4 ,) reg>d to ! la/1 :i* is ( imm5se use 9 ! laboratory1 !re happ5 to be at lea/ two excell5t & h&y books1 viz4 ,sauni]'s ,wat*mak]s' ,h&book1 ,trippl91 ,london1 #ahib2 & ,britton's ,wat*mak]s' ,diction>y & ,guide4 ,) reg>d to c>p5t]+1 turn+1 & blacksmi?+1 almo/ any "o :o s desires c obta9 a little practical exp]i5ce 9 any village4 ,a %ort *apt] has be5 devot$ to glass-bl[+1 9 spite ( !re be+ an excell5t & h&y book by ,mr4 ,%5/one 7,! ,me?ods ( ,glass-bl[+1 ,riv+ton7 on ! subject already 9 exi/5ce4 ,! reason = ?is exception lies 9 ! fact t ! writ]'s me?ods diff] consid]ably f ^? advocat$ by ,mr4 ,%5/one4 ,! *apt] on opticians' "w has _h to be compress$ to an ext5t :i* is undesirable 9 deal+ ) s complex & delicate an art1 b x is hop$ t x w prove a suffici5t introduction = laboratory purposes4 ,9 ?is matt] ! writ] is "u great obligations to 8 fri5d & assi/ant1 ,mr4 ,james ,cook1 ,f4,r4,a4,s1 :o gave him 8 fir/ lessons 9 l5s-mak+ "s tw5ty ye>s ago4 ,to ,mr4 ,john ,a4 ,bra%e> ( ,allegh5y1 ,pa1 ?anks are due = mu* miscellane\s in=mation on optical "w1 :i* is includ$ v]batim 9 ! text1 "s ( x conta9$ orig9ally 9 pr9t$ pap]s1 & "s mo/ k9dly communicat$ to ! writ] = ! purpose ( ?is book4 ,9 p>ticul>1 ! writ] w\ld ?ank ,mr4 ,bra%e> = 8 g5]\sly accord$ in=mation z to ! production ( ^? flat surfaces = :i* he is s ju/ly fam\s4 ,! writ] is also indebt$ to ,mr4 ,a4 ,e4 ,k5nelly = "s in=mation z to ,am]ican practice 9 ! use ( insulat+ mat]ial = electrical "w1 & to 8 fri5ds ,mr4 ,j4 ,a4 ,pollock & ,dr4 ,c4 ,j4 ,m>t9 = _m valuable sugge/ions4 ,= ! illu/rations ?anks are due to ,mrs4 ,?relfall & ,mr4 ,james ,cook4 ,) reg>d to matt]s :i* h come to ! writ]'s k by 8 be+ specifically in/ruct$ 9 !m f "t to "t1 due ackn[l$gm5t is1 x is hop$1 made 9 ! text4 ,) reg>d to ! "q z to :at matt]s might be includ$ & :at omitt$1 ! g5]al rule has be5 to include in=mation :i* ! au?or has obta9$ ) difficulty1 & to leave on "o side t :i* he has m easily atta9$4 ,all ! unities h be5 consi/5tly outrag$ by a delib]ate use ( ! ,engli% & metric sy/ems side by side4 ,s long z all ! mat]ials = me*anical processes h to be pur*as$ to specifications 9 in*es & feet1 x is impossible to use ! c5timetre consi/5tly )\t introduc+ inconv5i5ce4 ,h[ev]1 ev]ybody ought to1 & probably does1 use ei!r sy/em ) equal facility4 ,no attempt has be5 made at %[+ h[ "w c be done )\t tools4 ,?\gh1 no d\bt1 a great deal c be done ) inf]ior appliances :]e great economy ( money & none ( "t is an object1 ! writ] has long felt v /rongly t ,engli% physical laboratory practice has gone too f> 9 ! direction ( />v+ ! work%op1 & he does n wi%1 ev5 indirectly1 'to give any c\nt5ance to su* a mi/ak5 policy4 ,physical rese>* is too difficult 9 itself1 & /ud5ts' "t is too valuable1 = x to be remun]ative to "w ) insuffici5t appliances4 ,9 conclusion1 ! writ] w\ld ask 8 read]s to reg>d ! book to "s ext5t z t5tative1 & z a means to ! procur+ & organis+ ( in=mation be>+ ^u laboratory arts4 ,any in=mation :i* c be giv5 w be always ?ankfully receiv$1 & ! au?or h]eby reque/s any read] :o may happ5 to le>n some?+ ( value f ! book to communicate any special in=mation he may possess1 s t x may be ( use to o!rs %\ld ano!r edition ev] be call$ =4 ,,*apt] ,i ,,h9ts ,,on ,,! ,,manipulation ,,( ,,glass ,,& ,,on ,,glass-,,bl[+ ,,= ,,laboratory ,,purposes #a4 ,,! art ( glass-bl[+ has ! conspicu\s advantage1 f ! po9t ( view ( lit]>y pres5tation1 ( be+ to a great ext5t incommunicable4 ,z 9 ! case ( o!r delightful arts--su* z ^? treat$ ( 9 ! ,badm9ton ,libr>y1 = in/ance--! mo/ t c be done by writ+ is to indicate suitable me?ods & to po9t out precautions :i* exp]i5ce has %[n to be necess>y1 & :i* are n always obvi\s :5 ! art is fir/ approa*$4 ,x is n ! object ( ?is "w to deal ) ! art ( glass-bl[+ or any o!r art aft] ! mann] befitt+ a complete treatise1 9 :i* e =m ( practice is rightly includ$4 ,on ! contr>y1 x is my wi% to avoid ! pres5tation ( alt]native me?ods4 ,i consid] t ! pres5tation ( alt]native me?ods w\ld1 = my pres5t purpose1 be a positive disadvantage1 = x w\ld swell ?is book to an outrage\s size2 & to beg9n]s--,i speak f exp]i5ce--too lavi% a treatm5t acts r by way ( obscur+ ! po9ts to be aim$ at ?an z a means ( enlight5m5t4 ,! /ud5t (t5 does n "k :i* p>ticul> bit ( advice to foll[1 & obta9s ! errone\s idea t great art has to be br\ght to be> to enable him to accompli% :at is1 aft] all1 mo/ likely a p]fectly simple & /raight=w>d op]ation4 ,?is be+ und]/ood1 x might p]haps be expect$ t ,i %\ld describe no?+ b ! v be/ me?ods = obta9+ any propos$ result4 ,su*1 ( c\rse1 has be5 my aim1 b x is n likely t ,i h succe$$ 9 e case1 or ev5 9 ! majority ( cases1 = ,i h conf9$ myself to giv+ su* directions z ,i "k f my own p]sonal exp]i5ce w1 if prop]ly c>ri$ out1 lead to ! result claim$4 ,9 ! few cases 9 :i* ,i h to ref] to me?ods ( :i* ,i h no p]sonal exp]i5ce1 ,i h endeav\r$ to give ref]5ces 7usually tak+ ! =m ( an ackn[l$gm5t71 s t an idea ( _! value may be =m$4 ,all me?ods n p>ticul>is$ may be assum$ by ! read] to h come )9 my p]sonal exp]i5ce4 #b4 ,return+ to glass-bl[+1 we may note t two =ms ( glass-bl[+ are kn[n 9 ! arts1 ,pot bl[+ & ,table bl[+4 ,9 ! =m] case l>ge quantities ( fluid metal 7te*nical t]m = melt$ glass7 are assum$ to be available1 & z ?is is seldom ! case 9 ! laboratory1 & z ,i h n yet felt ! want ( su* a supply1 ,i %all deal only ) table bl[+4 ,=tunately !re is a conv5i5t book on ?is subject1 by ,dr4 ,%5/one 7,riv+tons71 s t :at ,i h to say w be z brief z possible1 consi/5t ) suffici5cy = ev]yday "w4 ,z a matt] ( fact !re is n v mu* to say1 = if ev] !re 0 an art 9 :i* manual dext]ity is ( ! fir/ & la/ importance1 t art is glass-work+4 ,i d n ?9k t a man c become an accompli%$ glass-bl[] f book in/ructions m]ely--at all ev5ts1 n )\t mu* unnecess>y lab\r1--b he c le>n to d a numb] ( simple ?+s :i* w make an enorm\s diff]5ce to him bo? z reg>ds ! progress ( 8 "w & ! /ate ( 8 pocket4 #c4 ,! fir/ ?+ is to select ! glass4 ,9 g5]al1 x w suffice to pur*ase tubes & rods2 9 ! case :]e l>ge pieces 7su* z ! bulbs ( ,geissl] pumps7 h to be specially prep>$ by pot-bl[+1 ! /ud5t w h to obs]ve precautions to be m5tion$ lat] on4 ,!re are ?ree k9ds ( glass mo/ g5]ally employ$ 9 laboratories4 #d4 ,s(t ,soda ,glass1 obta9$ = ! mo/ "p f factories 9 ,?ur+ia1 & g5]ally us$ 9 assembl+ *emical app>atus4--,?is glass is *eap1 & easily obta9able f any l>ge firm ( app>atus deal]s or *emi/s4 ,x %\ld on no acc\nt be pur*as$ f small druggi/s1 = ! foll[+ reasons3- 7a7 ,x is usually absurdly de> :5 obta9$ 9 ?is way4 7b7 ,x is g5]ally made up ( selections ( diff]5t age & diff]5t composition1 & pieces ( diff]5t composition1 ev5 if ! diff]5ce is slight1 w n fuse toge!r & rema9 toge!r unless jo9$ 9 a special mann]4 7c7 ,x is g5]ally old1 & ?is k9d ( glass (t5 devitrifies ) age1 & is !n useless = bl[pipe "w1 ?\gh x may be b5t suffici5tly = assembl+ *emical app>atus4 ,devitrifi$ glass looks fro/y1 or1 9 ! e>li] /ages1 appe>s to be cov]$ by cobwebs1 & is easily pick$ out & reject$4 #e4 ,x might be imag9$ t ! devitrification w\ld disappe> :5 ! glass is heat$ to ! fus+ po9t2 & s x does to a great ext5t1 b = _m op]ations "o only requires to s(t5 ! glass1 & ! devitrification (t5 p]si/s up to ?is temp]ature4 ,my exp]i5ce is t d5itrifi$ glass is also m likely to crack 9 ! flame ?an good new glass1 ?\gh ! diff]5ce 9 ?is respect is n v /rongly m>k$ ) n>r[ tubes4 #f4 ,fl9t ,glass4 ,magnific5t fl9t glass is made bo? 9 ,engl& & ,france4 ,! ,engli% exp]im5t] w probably pref] to use ,engli% glass1 &1 if he is wise1 w buy a good deal at a "t1 s9ce x does n appe> to devitrify ) age1 & uni=mity is !reby m likely to be secur$4 ,i h obta9$ uni=mly good results ) glass made by ,messrs4 ,p[ell ( ,:itefri>s1 b ,i d>esay equally good glass may be obta9$ else:]e4 ,= g5]al purposes fl9t glass is va/ly sup]ior to ! s(t soda m5tion$ above4 ,9 ! fir/ place1 x is v mu* /rong]1 & also less liable to crack :5 heat$--n alone :5 x is new1 b also1 & especially1 aft] x has be5 p>tly work$4 ,app>atus made ( fl9t glass is less liable to crack & break at places ( unequal ?ickness ?an if made ( soda glass4 ,?is is n ( mu* importance :]e small pieces ( app>atus only are conc]n$1 because ^! c g5]ally be fairly anneal$2 & if ! "w is well done1 ! ?ickness w n be unev54 ,x is a diff]5t matt] :]e l>ge pieces ( app>atus1 su* z connections to ,geissl] pumps1 are conc]n$1 = ! glass has (t5 to be work$ p>tly 9 situ1 & c only be imp]fectly anneal$4 ,jo9ts made betwe5 specim5s ( diff]5t composition are mu* m likely to /& ?an :5 fa%ion$ 9 soda glass4 ,inde$1 if x is necess>y to jo9 two bits ( soda glass ( diff]5t k9ds1 x is bett] to sep>ate !m by a %ort l5g? ( fl9t glass2 !y are m likely to rema9 jo9$ to x ?an to ea* o!r4 ,a p>ticul> v>iety ( fl9t glass1 kn[n z :ite enamel1 is p>ticul>ly suitable = ?is purpose1 &1 inde$1 may be us$ practically z a cem5t4 #g1 ,x is1 h[ev]1 :5 ! necessity ( alt]+ or repair+ app>atus complicat$ by jo9ts arises t ! advantage ( fl9t glass is mo/ app>5t4 ,a crack any:]e ne> to a side1 or ins]t$ jo9t1 c sc>cely ev] be repair$ 9 ! case ( soda glass app>atus1 ev5 :5 ! glass is q ?9 & ! dim5sions small4 ,x %\ld also be m5tion$ t fl9t glass has a mu* m brilliant appe>ance ?an soda glass4 ,( c\rse1 !re is a consid]able diff]5ce betwe5 diff]5t k9ds ( fl9t glass z to ! melt+ po9t1 & ?is may acc\nt = ! div]g5cy ( ! /atem5ts usually met ) z to its fusibility comp>$ ) t ( soda glass4 ,! k9d ( fl9t glass made by ,messrs4 ,p[ell becomes di/9ctly s(t soon aft] x is hot en\gh to be appreciably lum9\s 9 a d>k5$ room1 & at a :ite heat is v fluid4 ,?is fluidity1 ?\gh ( advantage to ! practis$ work]1 is likely to give a beg9n] "s tr\ble4 #h4 ,z aga9/ ! advantages enum]at$1 !re are "s drawbacks4 ,! "o :i* w fir/ /rike ! /ud5t is ! t5d5cy ( ! glass to become r$uc$ 9 ! flame ( ! bl[-pipe4 ,?is c be got ov] by prop] adju/m5t ( ! flame1 z w be expla9$ lat] on4 ,a m s]i\s drawback 9 exact "w is ! foll[+4 ,9 mak+ a jo9t ) lead glass x is q possible to neglect to fuse ! glass completely toge!r at e po9t2 9 fact1 ! jo9t w /& p]fectly well ev5 if x be left ) a hole at "o side1 a ?+ :i* is q impossible ) s(t soda glass1 or is at lea/ exce$+ly unusual4 ,an accid5t ( ?is k9d is p>ticul>ly likely to happ5 if ! glass be at all r$uc$4 ,h5ce1 if a jo9t does n crack :5 cold1 ! presumption is1 9 ! case ( soda glass1 t ! jo9t is p]fectly made1 & w n all[ ( any leak2 b ?is is n ! case ) fl9t glass1 = :i* reason all jo9ts betwe5 fl9t glass tubes require ! mo/ m9ute exam9ation be=e !y are pass$4 ,if !re are any air bubbles 9 ! glass1 especial c>e mu/ be ex]cis$4 #i4 ,h>d or ,bohemian1 ,glass4 ,?is is1 ( c\rse1 us$ :]e high temp]atures are to be employ$1 & also 9 c]ta9 cases :]e its comp>ative insolubility 9 wat] is ( importance4 ,x is v unusual = ! inve/igator to h to make complicat$ app>atus f ?is glass4 ,fus$ jo9ts may be made betwe5 h>d glass & fl9t glass )\t us+ enamel1 & ?\gh !y (t5 break 9 ! c\rse ( "t1 /ill !re is no reason aga9/ _! employm5t1 provid$ ! "w be done prop]ly1 & !y are n requir$ to la/ too long4 #aj4 ,on ! ,*oice ( ,sizes ( ,glass ,tube4 ,x w be f\nd t = g5]al purposes tubes ab\t "o-qu>t] in* 9 inside diamet]1 & f "o-tw5tie? to "o-=tie? ( an in* ?ick1 are mo/ 9 dem&4 ,"s v ?9 soda glass ( ^! dim5sions 7s-call$ cyl9d] tubes7 w be f\nd v h&y = _m purposes4 ,= physico-*emical "w a good supply ( tub+1 f "o-half to ?ree-qu>t]s ( an in* inside diamet]1 & f "o-tw5tie? to "o-eigh? in* ?ick1 is v necess>y4 ,a few tubes up to ?ree in*es diamet]1 & ( v>i\s ?icknesses1 w also be requir$ = special purposes4 ,!rmomet] & b>omet] tub+ is occasionally requir$1 ! latt]1 by ! way1 mak+ p>ticul>ly bad b>omet]s4 ,! !rmomet] tub+ %\ld be ( all sizes ( bore1 f ! f9e/ obta9able up to t :i* has a bore ( ab\t "o-sixte5? ( an in*4 ,glass rods v>y+ f ab\t "o-tw5tie? ( an in* 9 diamet] up to1 say1 half an in* w be requir$1 also two or ?ree /icks ( :ite enamel glass = mak+ jo9ts4 ,to facilitate *oice1 !re is app5d$ a diagram ( sizes f ! catalogue ( a reliable ,g]man firm1 ,messrs4 ,desaga ( ,heidelb]g1 & ! exp]im5t] w be able to see at a glance :at sizes ( glass to ord]4 ,x is a good plan to /ock ! l>ge/ & smalle/ size ( ea* mat]ial z well z ! mo/ useful work+ sizes4 ,fig4 #a4 #aa4 ,te/+ ,glass4 ,reject glass :i* has lumps or knots1 is obvi\sly conical1 or has long drawn-out bubbles runn+ ?r\gh ! sub/ance4 ,if a scrat* be made on ! surface ( a glass tube1 & "o end ( ! scrat* be t\*$ by a v f9e po9t ( fus$ glass1 say n m ?an "o-sixte5? in* 9 diamet]1 ! tube1 h[ev] l>ge x is 7)9 reason71 ought to crack 9 ! direction ( ! scrat*4 ,if a big crack =ms & does n run /raight1 b t5ds to turn longitud9ally1 x is a sign t ! glass is ill anneal$1 & no?+ c be done ) x4 ,if su* glass be hit ^u 9 ! c\rse ( bl[-pipe "w1 x is inadvisable to wa/e "t ^u x2 ! be/ plan is to reject x at once1 & save x = "s exp]im5t :]e x w n h to be heat$4 ,! %orte/ way ( select+ glass is to g to a good firm1 & let x be und]/ood t if ! glass proves to be badly anneal$ x w be return$4 ,?\gh x 0 /at$ above t ! glass %\ld n be di/9ctly conical1 ( c\rse all[ance mu/ be made = ! l5g? ( ! pieces1 &1 on ! o!r h&1 a few highly conical tubes w be ( imm5se s]vice 9 special cases1 & a small supply ( su* %\ld be includ$4 ,! glass1 z x is obta9$1 %\ld be plac$ 9 a rack1 & cov]$ by a clo? to r$uce ! quantity ( du/ f9d+ its way into ! tubes4 ,x has be5 /at$ by ,pr(essor ,o/wald t tubes :5 re>$ up on end t5d to b5d p]man5tly4 ,i h n notic$ ?is ) lead glass well support$4 ,ea* diff]5t supply %\ld be kept by itself & c>efully describ$ on a label pa/$ on to ! rack1 & tubes f diff]5t lots %\ld n be us$ = critical welds4 ,?is rem>k is m important 9 ! case ( soda ?an ( lead glass4 ,9 ! case ( v f9e !rmomet] tubes x w be advisable to cov] ! ends ) a little melt$ %ellac1 or1 9 special cases1 to obta9 ! tubes seal$ f ! works4 ,soda glass c g5]ally be got 9 r long] l5g?s ?an lead glass2 ! long] ! l5g?s are ! bett]1 = ! wa/e is less4 ,x is useful to be able to di/+ui% ! diff]5t k9ds ( glass by ! col\r4 ,?is is be/ obs]v$ by look+ t[>ds a bright surface along ! :ole l5g? ( ! tube & ?r\gh ! glass4 ,lead glass is yell[1 soda glass is gre51 & h>d glass purple 9 ! samples 9 my laboratory1 & ,i expect ?is is practically true ( mo/ samples4 ,footnote3 ,"s new lead glass ,i h is also almo/ purple 9 hue4 ,if any d\bt exi/s z to ! k9d ( glass1 x may be te/$ at once 9 ! bl[-pipe flame1 or by a mixture ( oils ( diff]5t refractive indices1 z w be expla9$ lat]4 #ab4 ,! "q ( ! solubility ( glass 9 reag5ts is "o ( great importance 9 accurate "w1 ?\gh x does n always meet ) ! att5tion x des]ves4 ,x is impossible "h to g into ! matt] ) suffici5t detail1 & ! read] is !re=e ref]r$ to ! ,ab/racts ( ! ,*emical ,society1 p>ticul>ly = ! ye>s #ahhi & #ahib4 ,! memoir by ,f4 ,kohlraus*1 ,wi$4 ,ann4 xliv1 %\ld be consult$ 9 ! orig9al4 ,! foll[+ po9ts may be not$4 ,a me?od ( te/+ ! quality ( glass is giv5 by ,mylius 7,c4 ,s4 ,j4 ,ab/racts1 #ahhi1 p4 #edi71 & x is /at$ t ! resi/ance ( glass to ! action ( wat] c g5]ally be mu* increas$ by leav+ x 9 contact ) cold wat] = sev]al days1 & !n heat+ x to #cjj to #djj ,c4 ,?is improvem5t seems to be due to ! =mation ( a lay] ( moi/ silica on ! surface1 & its subsequ5t cond5sation into a resi/+ lay] by ! heat+4 ,mylius 7,c4 ,s4 ,j4 ,ab/racts1 #ahib1 p4 #daa71 & ,web]1 & ,sau] 7,c4 ,s4 ,j4 ,ab/racts1 #ahib1 p4 #daj7 h also %[n t ! be/ glass = g5]al *emical purposes consi/s (3 ,silica1 #g to #h p>ts ,lime1 #a "p ,alkali1 #a4e to #a4a p>ts4 ,?is is practically ,bohemian tube glass4 ,! exact results are giv5 9 ! ,b]i*te ( ! ,g]man ,*emical ,society1 vol4 xxv4 ,an excell5t acc\nt ( ! prop]ties ( glass w be f\nd 9 ,grove's edition ( ,mill]'s ,elem5ts ( ,*emi/ry4 #ac4 ,clean+ ,glass ,tubes4 ,?is is "o ( ! mo/ important arts 9 *emi/ry4 ,if ! tubes are new1 !y are g5]ally only soil$ by du/1 & c be clean$ fairly easily--fir/ by pu%+ a bit ( cotton wa/e ?r\gh ) a cane1 or pull+ a rag ?r\gh ) /r+--& !n wa%+ ) s& & comm]cial hydro*loric acid4 ,i h he>d ( glass becom+ scrat*$ by ?is process1 & break+ 9 consequ5ce :5 heat$1 b h nev] myself exp]i5c$ ?is inconv5i5ce4 ,9 ,g]man laboratories little bits ( bibul\s pap] are sometimes us$ in/ead ( s&2 !y soon break into a pulp1 & ?is pulp has a slightly sc\r+ action4 ,z soon z ! visible impurities are remov$ & ! tube :5 wa%$ looks bright & clean1 x may be wip$ on ! outside & held p]p5dicul>ly s z to all[ ! wat] film to dra9 d[n4 ,if ! tube be greasy 7& p]haps 9 o!r cases7 x w be obs]v$ t z ! film gets ?9n] ! wat] beg9s to break away & leave dry spots4 ,= accurate "w ?is grease1 or :atev] x is1 mu/ be remov$2 & aft] try+ _m plans = _m ye>s1 ,i h come back to ! me?od ,i fir/ employ$1 viz4 boil+ out ) aqua regia4 ,= ?is purpose1 close "o end ( ! tube by a cork 7bett] ?an a rubb] bung1 because *eap]71 & half fill ! tube ) aqua regia2 !n1 hav+ not$ ! greasy places1 proce$ to boil ! liquid 9 contact ) ! glass at ^! po9ts1 & 9 ! case ( v ob/9ate dirt--su* z l+]s r\nd a fus$ jo9t :i* has be5 made betwe5 undu/$ tubes--leave ! :ole affair = twelve h\rs4 ,if ! greas9ess is only slight1 !n simply %ak+ ) hot aqua regia w (t5 remove x1 & ! aqua regia is conv5i5tly heat$ 9 ?is case by ! addition ( a little /rong sulphuric acid4 ,! sp5t aqua regia may be put into a bottle4 ,x is g5]ally q good en\gh = ! purpose ( wa%+ glass vessels ) s&1 z above expla9$4 ,h[ev] c>efully a tube is clean$ be=e be+ subject$ to bl[pipe op]ations1 x w be f\l$ :]ev] !re is an op5+ dur+ ! process ( heat+1 unless ! extreme tip only ( an oxidis+ flame be employ$4 ,ev5 ?is %\ld n be tru/$ too implicitly unless an oxygas or hydrog5 flame is employ$4 ,:5 a tube or piece ( app>atus has be5 clean$ by acid1 s t on clamp+ x v]tically1 dry spaces d n appe>1 x may be r9s$ ) plat9um di/ill$ wat] & left to dra91 ! du/ be+1 ( c\rse1 kept out by plac+ a bit ( pap] r\nd ! top4 ,= accurate "w wat] ?us prep>$ is to be pref]r$ to any?+ else4 ,:5 ! glass is v clean int]f]5ce col\rs w be notic$ z ! wat] dries away4 ,c>efully-purifi$ alcohol may 9 "s cases be employ$ :]e x is desir$ to dry ! tube or app>atus quickly4 ,9 ?is case an alcohol wa% bottle %\ld be us$1 & a little alcohol squirt$ into ! top ( ! tube all r\nd ! circumf]5ce4 ,! wat] film drags ! alcohol aft] x1 & by wait+ a few m9utes & !n add+ a few m drops ( alcohol1 ! wat] may be practically entirely remov$1 especially if a bit ( filt] pap] be held aga9/ ! l[] end ( ! tube4 ,x is cu/om>y 9 "s laboratories to use e!r = a f9al r9se1 b unless ! e!r is fre%ly di/ill$ & v pure1 x leaves a di/9ct organic residue4 ,:5 no m liquid c be caus$ to dra9 away1 ! tube may be dri$ by heat+ x along its l5g?1 beg9n+ at ! top 7to get ! advantage ( ! r$uction ( surface t5sion71 & s on all d[n4 ,x w !n be possible to mop up a little m ( ! r9s+ liquid4 ,:5 ! tube is ne>ly dry a loose plug ( cotton wool may be ins]t$ at ! bottom4 ,! wool mu/ be put 9 s t ! fibres lie on an ev5 surface inside ! tube1 & ! wool mu/ be bl[n free f du/4 ,ord9>y cotton wool is useless1 f be+ du/y & ! fibres %ort1 & ! same rem>k applies to wadd+4 ,use no?+ b :at is kn[n z m$icat$ cotton wool ) a good long fibre4 ,! tube w usually soon dry ( itself :5 ! cov] is lift$ an in* or s4 ,if wat] has be5 us$1 ! air-curr5t may be assi/$ by means ( ! wat]-pump1 ! air be+ suck$ f ! top1 s t ! wool has an opportunity ( act+ z a du/ filt]2 a v sl[ /ream ( air only mu/ be employ$4 ,= connect+ ! tube to ! pump1 a bit ( ,india-rubb] tube ab\t an in* 9 diamet]1 ) a bore ( ab\t "o-eigh? ( an in*1 may be employ$4 ,! end ( ! rubb] tube is m]ely press$ aga9/ ! edge ( ! glass4 ,^! rem>ks apply1 ) suitable modification1 to all k9ds ( f9i%$ app>atus hav+ two op5+s4 ,= flasks & s on1 x is conv5i5t to employ a bl[+ app>atus1 du/ be+ avoid$ by ins]t+ a p]man5t plug ( cotton wool 9 "o ( ! lead+ tubes4 ,! effici5cy ( ?is me?od is greatly increas$ by us+ ab\t "o foot ( ?9 copp] tube1 b5t into a helix1 & heat$ by means ( a ,buns5 burn]2 ! hot air 7previ\sly filt]$7 is pass$ directly into ! flask1 bottle1 or :atev] ! app>atus may be4 ,?is has prov$ s conv5i5t t a copp] coil is n[ p]man5tly fa/5$ to ! wall 9 "o ( ! rooms ( my laboratory4 ,! above in/ructions indicate great] ref9em5t ?an is 9 g5]al necess>y or prop] = tubes t h to be aft]w>ds work$ by ! bl[-pipe4 ,9 ! majority ( cases all t is necess>y is to remove ! du/1 & ?is is pref]ably done by a wad ( cotton wa/e 7:i* does n leave %r$s l cotton wool71 foll[$ by a bit ( bibul\s filt] pap]4 ,i w\ld especially w>n a beg9n] aga9/ neglect+ ?is precaution1 = 9 ! process ( bl[+1 ! du/ und]goes "s *ange at ! heat$ p>ts ( ! app>atus1 & =ms a p>ticul>ly ob/9ate k9d ( dirt4 ,9 special cases ! me?ods ,i h advocat$ = remov+ dirt & dry+ )\t cov]+ ! damp surfaces ) du/ are inadequate1 b an exp]im5t] :o has got to t /age w h no?+ to le>n f su* a "w z ?is4 #ad4 ,! ,bl[-pipe4 ,i suppose a small book might easily be writt5 on ?is subject b :at ,i h to say--9 accordance ) ! limitation impos$--w be brief4 ,= work+ lead glass ,i nev] use any?+ b an oxygas bl[-pipe1 except = v l>ge "w1 & %\ld nev] dream ( us+ any?+ else4 ,( c\rse1 to a /ud5t :o requires practice 9 ord] to atta9 dext]ity ?is plan w\ld be a good deal too de>4 ,my advice to su* a "o is--procure good soda glass1 & "w x by means ( a modification ( a gas bl[-pipe1 to be describ$ directly4 ,! ,flet*]'s bl[-pipes on long /ems are g5]ally v inconv5i5t4 ,! flame %\ld n be m ?an #e or #f in*es f ! work+ table at mo/1 especially = a beg9n]1 :o ne$s to re/ 8 arms on ! edge ( ! table to secure /ead9ess4 ,! k9d ( oxygas bl[-pipe ,i f9d mo/ conv5i5t is indicat$ 9 ! sket*4 7,fig4 #b7 ,i l to h two nozzles1 :i* w slip on & (f1 "o ) a jet ( ab\t #j4jce in* 9 diamet]1 ! o!r ( ab\t d\ble ?is dim5sion4 ,! oxyg5 is l$ into ! ma9 tube ( ! bl[-pipe by ano!r tube ( mu* small] diamet]1 conc5tric ) ! ma9 tube 7,fig4 #c1 at ,a74 ,! oxyg5 is mix$ ) ! gas dur+ its escape f ! inn] tube1 :i* is pi]c$ by a numb] ( f9e holes = ! purpose1 ! extreme end be+ clos$ up4 ,! inn] tube may run up to )9 half an in* ( ! po9t :]e ! cap c>ry+ ! nozzle jo9s ! l>g] tube4 ,fig4 #b4 ,fig4 #c4 ,if x is desir$ to use ! bl[-pipe = work+ glass :i* is already fix$ 9 position to a support1 x w be f\nd v advantage\s to use a hook$ nozzle4 ,! nozzle %[n 9 ! sket* is n hook$ en\gh = ?is "w1 :i* requires t ! flame be direct$ 'backw>ds t[>ds ! work]4 ,) a little practice su* a flame may be us$ p]fectly well = bl[+ op]ations on ! table1 z well z = gett+ at ! back ( fix$ tubes4 ,to w>m up ! glass1 ! gas supply is turn$ full on1 & en\gh oxyg5 is all[$ to pass 9 to cle> ! flame4 ,! "w is held 9 front (1 b n t\*+1 ! flame1 until x is suffici5tly hot to be> mov+ into ! flame itself4 ,!1 "w is expos$ to ?is flame until1 9 ! case ( lead glass1 traces ( r$uction beg9 to appe>4 ,:5 ?is po9t is rea*$ ! oxyg5 tap is ?r[n wide op54 ,i g5]ally regulate ! pressure on ! bags1 s t "u ^! circum/ances ! flame is r ov]f$ ) oxyg54 ,?is condition is easily recognis$1 z foll[s4 ,! flame %r9ks d[n to a v small compass1 & ! inn] blue cone almo/ disappe>s2 also fla%es ( yell[ light beg9 to %[ !mselves--a ?+ :i* does n occur :5 ! proportions ( ! gases are adju/$ = maximum heat+ effect4 ,= _m purposes ! small dim5sions ( ! flame r5d] x v conv5i5t1 & ! high temp]ature :i* c be atta9$ at exact spots enables glass to be fus$ toge!r aft] a c]ta9 am\nt ( mix+1 :i* is an enorm\s advantage 9 fus+ lead glass on to h>d glass4 ,! lead glass %\ld n be heat$ hot en\gh to burn1 b1 %ort ( ?is1 ! m fluid x is ! bett] = jo9ts betwe5 dissimil> samples4 ,x w be notic$ t ! bl[-pipe c be rotat$ ab\t a v]tical axis s z to ?r[ ! flame 9 v>i\s directions4 ,?is is (t5 indisp5sable4 #ae4 ,9 g5]al ! oxyg5 flame does n require to be deliv]$ "u s high a pressure z = ! production ( a lime light4 ,9 ,engl&1 ,i presume1 mo/ exp]im5t]s w obta9 _! oxyg5 ready prep>$ 9 bottles1 & w n h to und]go ! annoyance ( fill+ a bag4 ,if1 h[ev]1 a bag is us$1 & x has "s advantages 7! valves ( bottles be+ g5]ally /iff71 ,i f9d t a pressure produc$ by plac+ ab\t two hundr$weight 7conv5i5tly divid$ into f\r fifty-six p\nd weights7 on bags measur+ #c' x #b'f x #b' 7at ! ?ick] end7 does v well4 ,to fill su* a bag ) oxyg51 ab\t #gjj grms ( potassium *lorate is requir$4 ,if ! exp]im5t] desires to keep 8 bag 9 good ord]1 he mu/ purify 8 oxyg5 by wa%+ x ) a solution ( cau/ic soda1 & !n pass+ x ?r\gh a t[] ( pota% or soda 9 /icks1 &1 f9ally1 ?r\gh a calcium *loride t[]4 ,?is purify+ app>atus %\ld be p]man5tly set up on a bo>d1 s t x may be c>ri$ ab\t by ! att5dant to :]ev] x is requir$4 ,oxyg5 ?us purifi$ does n seem to injure a good bag--at lea/ dur+ ! fir/ six or sev5 ye>s3 ,9 ord] to r$uce ! annoyance ( prep>+ oxyg51 ! use ( ! usual ?9 copp] conical bottle %\ld be avoid$4 ,! mak]s ( /eel gas bottles provide retorts ( wr\ght iron or /eel = oxyg5-mak+1 & ^! d v well4 ,!y h ! incid5tal advantage ( be+ /rong en\gh to resi/ ! attacks ( a s]vant :5 a sp5t *>ge is be+ remov$4 ,! =m ( retort ref]r$ to is m]ely a l>ge tube1 clos$ at "o end1 & ) a screw c\pl+ at ! o!r2 ! dim5sions may be conv5i5tly ab\t #e in*es by #aj4 ,! screw ?reads %\ld be fill$ ) fireclay 7z recomm5d$ by ,f>aday7 be=e ! jo9t is screw$ up4 ,be=e pur*as+ a bottle ! exp]im5t] w d well to rememb] t unless x is ( suffici5tly small diamet] to g into 8 l>ge/ vice1 he w be inconv5i5c$ 9 screw+ ! top on & (f4 ,:y ^! affairs are n made ) union jo9ts1 z !y %\ld be1 is a "q :i* w p]haps be answ]$ :5 we le>n :y cork bor]s are /ill g5]ally made ( brass1 ?\gh /eel tube has long be5 available4 ,fig4 #d4 ,^! little matt]s may appe> v trivial--& s !y are--b ! pur*as] ( app>atus w g5]ally f9d t unless he looks aft] details himself1 !y w n be att5d$ to = him4 ,:e!r a union jo9t is provid$ or n1 let x be se5 t ! end ( ! deliv]y tube is ei!r small en\gh to fit a l>ge rubb] tube connection go+ to ! wa%-bottle1 or l>ge en\gh to all[ ( a cork c>ry+ a bit ( glass tube = ! same purpose to be ins]t$4 ,?is tube %\ld n be less ?an half an in* 9 inside diamet]4 ,nev] use a new bottle be=e x has be5 heat$ suffici5tly to get rid ( grease & c>bonace\s dirt4 ,a conv5i5t oxyg5-mak+ app>atus is %[n 9 ,fig4 #d1 :i* is drawn f life4 #af4 ,= l>ge bl[-pipe "w ) lead glass ,i recomm5d a sy/em ( f\r simple bl[-pipes1 9 accordance ) ! sket* annex$4 ,i fir/ saw ?is sy/em 9 op]ation 9 ! lamp factory ( ! ,we/+h\se ,electric ,company at ,pittsburg 9 #ahhi1 & s9ce !n ,i h se5 x us$ by an exce$+ly clev] trick glass-work] at a %[4 ,aft] try+ bo? ?is arrangem5t & ! bru% flame recomm5d$ by ,mr4 ,%5/one1 ,i consid] ! =m] ! m conv5i5t2 h[ev]1 ,i d>esay t ei!r c be made to "w 9 compet5t h&s1 b ,i %all "h describe only my own *oice4 ,footnote3 ,a bru% flame is "o :i* issues f ! bl[-pipe nozzle %ap$ l a bru%1 i4e4 x exp&s on leav+ ! jet4 ,x is produc$ by us+ a cyl9drical air jet or a conical jet ) a l>ge ap]ture1 say "o-eigh? ( an in*4 ,see ,fig4 #be4 ,z w be se51 ! bl[-pipe really consi/s ( f\r simple brass tube bl[-pipes ab\t ?ree-eigh?s ( an in* int]nal diamet] & #c in*es long1 ea* ) its gas & air tap & appropriate nozzle4 ,ea* bl[pipe c turn ab\t its support 7! gas-entry pipe7 to "s ext5t1 & ?is possibility ( adju/m5t is ( importance1 ,! air jets are m]ely bits ( v ev5 ?ree-sixte5?s in* glass tub+1 drawn d[n to conical po9ts1 ! jets !mselves be+ ab\t #j4jce in* diamet]4 ,fig4 #e4 ,! flames produc$ are ! long n>r[ bl[-pipe flames us$ 9 bl[-pipe analysis1 & arrang$ s z to consi/ mo/ly ( oxidis+ flame4 ,! air-supply does n require to be l>ge1 nor ! pressure high--#e to #aj in*es ( wat] w d--b x mu/ be v regul>4 ,! trick glass-bl[] ,i ref]r$ to employ$ a foot bell[s 9 connection ) a small weight$ gasomet]1 ! ,we/+h\se ,company us$ _! ord9>y air-bla/1 & ,i h g5]ally us$ a l>ge gas-hold] ) :i* ,i am provid$1 :i* is suppli$ by a ,roots bl[] work$ by an eng9e4 ,i h also us$ a velocity pump bl[]1 :i* may be pur*as$ among/ o!rs f ,g]h>dt ( ,bonn4 ,! arrangem5t acts bo? z a suck+ & bl[+ app>atus1 & is furni%$ ) two manomet]s & prop] taps1 etc4 ,z ,i h reason to "k t arrangem5ts ( ?is k9d "w v ill unless really well made1 ,i v5ture to add t ! ,g]h>dt arrangem5t to :i* ,i ref] is ,no4 #bci 9 8 catalogue1 & co/s ab\t ?ree p\nds4 ,x h>dly gives en\gh air1 h[ev]1 to "w f\r bl[-pipes1 & ! bla/ requires to be /eadi$ by pass+ ! air ?r\gh a vessel cov]$ ) a rubb] %eet4 ,9 default ( any ( ^! means be+ available1 "o ( ,flet*]'s foot-bl[]s may be employ$1 b x mu/ be work$ v regul>ly4 ,a table m\nt$ ) "o bl[-pipe made on ?is plan1 & work$ by a d\ble-act+ bell[s1 is recomm5d$ = /ud5ts' use4 ,= work+ fl9t glass1 ! air jet may be "o-eigh? ( an in* 9 diamet] & ! pressure high]--?is w give a bru% flame4 ,see ,fig4 #be4 ,x w be se51 on look+ at ! sket* ( ! bl[pipe sy/em1 t ! pair ( bl[-pipes f>!r f ! obs]v] c be caus$ to approa* or rec$e at w by means ( a h&le work+ a block on a slide4 ,x (t5 happ5s t aft] us+ all f\r bl[-pipes at once x is necess>y to h rec\rse to "o bl[-pipe only1 & to d ?is conv5i5tly & quickly is r an object4 ,n[1 9 my arrangem5t ,i h to turn (f bo? ! gas & air f ! f>!r sy/em1 & !n put 9 a bit ( asbe/os bo>d to prev5t ! nozzles be+ damag$ by ! flame or flames kept alight4 ,z ,i said be=e1 :5 "s exp]i5ce is ga9$1 glassbl[+1 becomes a v simple art1 & "w c be done "u circum/ances s disadvantage\s t !y w\ld entirely fru/rate ! ef=ts ( a beg9n]4 ,?is is n any excuse1 h[ev]1 = recomm5d+ inf]ior arrangem5ts4 ,consequ5tly1 ,i say t ! pipes lead+ 9 gas & air %\ld be all bran*es ( "o gas & "o air pipe1 9 s f> z ! two remote & "o proximate bl[-pipe are conc]n$1 & ^! pipes %\ld come up to ! table to ! "r h& ( ! op]ator1 & %\ld h ma9 taps at t po9t1 ea* ) a h&le at lea/ #b in*es long4 ,by ?is arrangem5t ! op]ator c in/antly turn d[n all ! bl[-pipes b "o1 :ile1 if ! inv]se op]ation is requir$1 all ! ?ree pipes c be />t$ at once4 ,footnote3 ,i f9d1 s9ce writ+ ! above1 t ,i h be5 anticipat$ 9 ?is recomm5dation by ,mr4 ,g4 ,s4 ,ram1 ,! ,inc&esc5t ,lamp & its ,manufacture1 p4 #aad4 ,! sep>ate air & gas taps mu/ be left = p]man5t regulation1 & mu/ n be us$ to turn ! supply on or cut x (f4 ,9 "s respects ?is bl[-pipe w be f\nd m easy to manage ?an an oxygas bl[-pipe1 = ! glass is n s readily br\ght to ! v fluid /ate1 & ?is w (t5 enable a beg9n] :o proce$s cauti\sly to d m ?an he c\ld ) ! m p[]ful in/rum5t4 ,?\gh ,i h m5tion$ glass nozzles = ! air supply1 !re is no difficulty 9 mak+ nozzles ( brass4 ,= ?is purpose let ! end ( a brass tube ( ab\t "o-eigh? ( an in* diamet] be clos$ by a bit ( brass wire previ\sly turn$ to a section z %[n 7,fig4 #f71 & !n bor$ by a drill ( ! requir$ diamet]1 say -4#jce in*4 ,x is mo/ conv5i5t to use too small a drill1 & to gradually op5 ! hole by means ( t beautiful tool1 ! wat*mak]'s broa*4 ,! edges ( ! jet %\ld be fre$ f burr by means ( a wat*mak]'s *amf]+ tool 7see ,sauni]'s ,wat*mak]'s ,h&-book1 ,trippl91 #ahhb1 p4 #bcb1 #cdb71 or by ! alt]nate use ( a slip ( ,kansas /one & ! broa*4 ,fig4 #f4 ,! con/ruction ( ?is bl[-pipe is s simple1 t 9 case any "o wi%es to use a bru% flame1 he c easily produce "o simply by *ang+ 8 air jets to bits ( ! same size 7say "o-eigh? to "o-sixte5? ( an in*7 tub+1 cut (f clean4 ,to insure success1 ! ends ( ! tubes mu/ be absolutely plane & regul>2 ! slighte/ inequality makes all ! diff]5ce 9 ! action ( ! in/rum5t4 ,if a jet is f\nd to be defective1 cut x d[n a little & try aga92 a clean-cut end is bett] ?an "o :i* has be5 gr\nd flat on a /one4 ,! end ( a tube may1 h[ev]1 be turn$ 9 a mann] h]eaft] to be describ$ s z to make an effici5t jet4 ,sev]al trials by cutt+ w probably h to be made be=e success is atta9$4 ,= ?is k9d ( jet ! air-pressure mu/ be greatly increas$1 & a l>ge ,flet*]'s foot-bl[] or1 bett] /ill1 a small d\ble-action bell[s work$ ) vig\r w be f\nd v suitable4 ,a fitt+ = ?is auxili>y bl[-pipe is %[n 9 ,fig4 #e at ,b4 ,pr(essor ,ro5tg5's discov]y has rec5tly made x necess>y to give m p>ticul> att5tion to ! work+ ( s(t soda glass1 & ,i h be5 oblig$ to supplem5t ! arrangem5ts describ$ by a table especially int5d$ = "w ) glass ( ?is "*4 ,! arrangem5t has prov$ s conv5i5t = g5]al "w t ,i give ! foll[+ p>ticul>s4 ,! table measures #e feet long1 #b feet #aa in*es wide1 & is #b feet #i in*es high4 ,fig4 #g4 ,x is provid$ ) a s+le gas socket1 into :i* ei!r a l>ge or small gas tube may be screw$4 ,! l>g] tube is #e4e in*es long & #j4ge ( an in* 9 diamet]4 ,! small] tube is ! same l5g?1 & half an in* 9 diamet]4 ,! axis ( ! l>g] tube is #c4e in*es above ! table at ! po9t ( support1 & is incl9$ to ! horizontal at an angle ( #ab4 ,! axis ( ! small] tube is #b4e in*es above ! surface ( ! table1 & is incl9$ to ! horizontal at ! same angle z ! l>g] "o4 ,! air jets are simply pieces ( glass tube held 9 position by corks4 ,! gas supply is regulat$ by a well-bor$ tap4 ,! air supply is regulat$ by tread+ ! bell[s--no tap is requisite4 ,! bell[s employ$ are ord9>y smi?s' bell[s1 measur+ #bb in*es long by #ac in*es wide 9 ! wide/ "p4 ,!y are weight$ by lead weights1 weigh+ #bf lbs4 ,! treadle is connect$ to ! bell[s by a small /eel *a91 = ! l5g? requires to be inv>iable4 ,z ! treadle only acts 9 =c+ air f ! l[] into ! upp] *amb] ( ! bell[s1 a weight ( #ac lbs4 is hung on to ! l[] cov]1 s z to op5 ! bell[s automatically4 ,! air jets :i* h hi!rto be5 f\nd conv5i5t are3 = ! small gas tube 7#a7 a tube #j4ab in* diamet] drawn d[n to a jet ( #j4jcb in* diamet] = small "w2 7#b7 pla9 tubes n drawn d[n ( #j4ad in*1 #j4abg in*1 & -#j4bde in* diamet]1 & = ! l>ge gas tube1 pla9 tubes up to #j4c in* 9 diamet]4 ,! table is plac$ 9 su* a position t ! op]ator sits ) 8 back to a w9d[ & has ! black calico scre5 9 front ( him & to 8 "r4 ,! object ( ! scre5 is to protect ! workman aga9/ draughts4 ,! table is purposely left unscre5$ to ! left ( ! workman1 s t long tubes may be treat$4 #ag4 ,o!r appliances :i* w be requir$ = glass-bl[+ are ( ! simple/ "*4 7#a7 ,small corks = clos+ ! ends ( tubes4 7#b7 ,s(t wax--a mixture ( bees' wax & res9 s(t5$ by l9se$ oil to ! prop] consi/5cy1 easily f\nd by trial1 also us$ = tempor>ily clos+ tubes4 7#c7 ,a bottle ( vasel9e = lubricat+4 7#d7 ,an old biscuit t9 fill$ ) asbe/os 9 %r$s1 & an asbe/os t[el or clo? = anneal+ glass aft] removal f ! flame4 ,z asbe/os absorbs moi/ure1 :i* w\ld defeat its use z an anneal+ mat]ial1 x mu/ be dri$ if necess>y4 7#e7 ,a ,glass-,cutt]'s ,knife4 ,?is is be/ made out ( a f9e ?ree-corn]$ file1 ) ! file tee? almo/ gr\nd out1 b n q2 x %\ld be ab\t #b in*es long4 ,aft] ! surface has be5 gr\nd sev]al times1 x may be necess>y to reh>d5 ! /eel4 ,?is is be/ done by heat+ to a full r$ & qu5*+ 9 m]cury4 ,! gr9d/one employ$ = %>p5+ ! knife %\ld be quick1 s z to leave a r\gh edge4 ,i h tri$ _m s-call$ glass knives made 9 ,g]many1 b1 ) "o exception1 !y 7 no?+ l s good z a small ,fr5* or ,%effield file4 ,9 ?is matt] ,i h ! support ( ,mr4 ,%5/one's exp]i5ce4 7#f7 ,a wire nail1 ab\t #b in*es long1 m\nt$ v accurately 9 a ?9 cyl9drical wood5 h&le ab\t #e in*es long by "o-qu>t] ( an in* diamet]1 or1 bett] /ill1 a bit ( p9ion wire #f in*es long1 ( :i* #a4e in*es are turn$ d[n z f> z ! cyl9drical core1 ,an old d5ti/s' *isel or fill+ tool is also a v good =m ( in/rum5t4 7#g7 ,a bit ( *>coal ab\t #c4e in*es long & #b wide1 & ( any ?ickness1 w be f\nd v useful 9 help+ to heat a v l>ge tube4 ,! *>coal block is provid$ ) a /\t wire h&le1 b5t 9 su* a mann] t ! block c be held close above a l>ge glass tube on :i* ! flames imp+e4 ,9 "s cases x is conv5i5tly held by a clip /&4 ,by ! use ( su* a slab ( *>coal ! temp]ature obta9able ov] a l>ge surface c be consid]ably increas$4 ,i h se5 a w9e-glass 7,v5etian %]ry-glass7 work$ on a table ) f\r bl[-pipes1 su* z is "h describ$1 ) ! help ( a block ( h>d wood held ov] ! heat$ glass1 & help+ ! atta9m5t ( a high temp]ature by its own combu/ion4 7#h7 ,sev]al retort /&s ) screw clips4 7#i7 ,"s blocks ( wood ab\t #e ,x #b ,x #b ) ,v-%ap$ not*es cut 9 f ! top4 7#aj7 ,a /rong pair ( pli]s4 7#aa7 ,an app>atus = clean+ & dry+ ! brea?1 :5 bl[+ directly by ! m\? is n all[able4 ,! app>atus consi/s ( a solid & heavy block ( wood support+ a calcium-*loride tube p]man5tly connect$ ) a tube ( phosphorus p5toxide divid$ into comp>tm5ts by plugs ( glass wool4 ,c>e %\ld be tak5 to arrange ^! tubes s z to occupy ! smalle/ space1 & to h ! /& p>ticul>ly /able4 ,! exit tube f ! phosphorus p5toxide %\ld be drawn d[n to =m a nozzle1 f1 say1 half an in* to "o-eigh? ( an in* 9 diamet]1 s z to easily fit almo/ any bit ( rubb] tube4 ,! entry to ! calcium *loride %\ld be p]man5tly fitt$ to ab\t a y>d ( f9e s(t rubb] tub+1 z light z possible4 ,! ends ( ?is tube %\ld t]m9ate 9 a glass m\?piece1 :i* %\ld n be too delicate4 ,z an additional precaution aga9/ du/1 ,i sometimes add a tube conta9+ a long plug ( glass wool1 betwe5 ! phosphorus p5toxide & ! deliv]y tube1 & also a tube conta9+ /ick pota% on ! entry side ( ! calcium *loride tube1 b x may safely be left to individual judgm5t to det]m9e :5 ^! additions require to be made4 ,9 practice ,i always keep ! affair set up ) ^! additions4 ,! communication betwe5 all ! p>ts %\ld be p]fectly free1 & ! tubes %\ld be ne>ly fill$ ) reag5ts1 s z to avoid hav+ a l>ge volume ( air to compress be=e a pressure c be got up4 ,! arrangem5t w be cle> by a ref]5ce to ,fig4 #h1 :i* illu/rates ! app>atus 9 use = jo9+ two long tubes4 ,i h tri$ bl[+-bags1 etc1 b1 on ! :ole1 pref] ! above arrangem5t1 =1 aft] a "t1 ! skill "o acquires 9 regulat+ ! pressure by bl[+ by ! m\? & lips is su* an advantage t x is n to be lightly =egone4 ,fig4 #h4 #ah4 ,! ,table4 ,! sy/em ( f\r bl[-pipes is1 ( c\rse1 a fixture4 ,9 ?is case ! table may be ab\t a y>d squ>e1 & may be cov]$ ) asbe/os mill-bo>d neatly laid d[n1 b ?is is n ess5tial4 ,! table %\ld h a rim runn+ r\nd x ab\t a qu>t] ( an in* high4 ,! tools %\ld be laid to ! "r ( ! work]1 & = ?is purpose ! bl[-pipes are conv5i5tly fix$ r to ! left ( ! c5tre ( ! table1 b n s f> z to make ! leg ( ! table come s close to ! op]ator z to make him uncom=table1 = a *e]ful & cont5t$ _s ought to be "p ( ! glass-work]'s outfit4 ,! mo/ conv5i5t height = a bl[-pipe table--) ! bl[-pipes ab\t #b in*es above ! table top--is #c feet #b in*es4 ,no?+ is s conv5i5t to sit ^u z a r\gh music-/ool ) a good range ( adju/m5t4 ,! advantage ( an adju/able seat lies 9 ! fact t = "s op]ations "o wants to be well ov] ! "w1 :ile 9 o!rs ! advantage ( re/+ ! arms aga9/ ! table is m important4 #ai4 ,special ,op]ations4 ,! prelim9>y to mo/ op]ations be=e ! bl[-pipe1 is to draw d[n a tube & pull x out to a f9e po9t4 ,?is is also ! op]ation on :i* a beg9n] %\ld ex]cise himself 9 ! fir/ in/ance4 ,i w suppose t x is desir$ to draw out a tube ab\t "o-qu>t] ( an in* 9 diamet]1 ) ! object ( clos+ x1 ei!r p]man5tly or tempor>ily1 & leav+ a h&le = future op]ations 9 ! %ape ( ! po9t1 ?9 en\gh to cool quickly & s n delay fur!r "w4 ,= ?is simple op]ation mo/ ( ! glass-bl[]'s skill is requir$4 ,! tube mu/ be grasp$ betwe5 ! fir/ f+] & ?umb ( bo? h&s1 & held s t ! "p to be op]at$ on lies ev5ly betwe5 ! two h&s4 ,! di/ance betwe5 ! op]ator's ?umbs may conv5i5tly v>y f #b4e to #d in*es4 ,releas+ ! grip ( ! left h&1 let ! op]ator assure himself ( 8 ability to easily rotate ! tube ab\t its axis--by ! "r ?umb & f+]--he w incid5tally obs]ve by ! feel :e!r ! tube is /raight or n4 ,a good deal ( progress c be made f ?is po9t be=e ! tube is heat$ at all4 ,! op]ator c acquire a habit ( in/9ctively rotat+ ! tube by bo? h&s1 h[ev] ! tube itself be mov$ ab\t 9 space1 or h[ev] x be pu%$ or pull$4 ,! habit ( con/ant & in/9ctive rotation is lit]ally ab\t "o-?ird ( ! :ole art ( glassbl[+4 ,x is unlikely1 h[ev]1 t ! beg9n] w discov] t he has n got ?is habit1 until a few failures draw 8 att5tion to x4 ,! glass tube be+ held 9 position lightly yet firmly1 & ! op]ator be+ sure t he feels com=table & at 8 ease1 & t ! bl[-pipe flame 7a s+le flame 9 ?is in/ance7 is well "u control1 ! prelim9>y heat+ may be comm5c$4 ,) a tube ( ! dim5sions giv5 ?is is a v simple affair4 ,turn ! air p>tly (f1 or bl[ g5tly1 to get a p>tly lum9\s gas flame2 hold ! tube ab\t an in* f ! end ( ?is flame1 & turn x r\nd & r\nd till x comm5ces to s(t54 ,9 ! case ( soda glass x is usual to employ ! gas flame only1 b ,i f9d t x is bett] 9 mo/ cases to use ! hot air ( a g5tly-bl[n flame1 r ?an h ! disadvantage ( ! soot deposit$ 9 ! alt]native op]ation4 ,:5 ! glass beg9s to s(t51 or ev5 be=e1 x may be mov$ "r into ! bl[-pipe flame1 & ! latt] may be prop]ly urg$4 ,x is n possible to give q explicit & def9ite in/ructions1 applicable to e case1 z to :5 ! "t is ripe = pass+ ! "w into ! flame1 b ! foll[+ notes w indicate ! g5]al rules to be obs]v$3- 7#a7 ,a ?ick tube mu/ be w>m$ m sl[ly & rais$ to a high] temp]ature ?an a ?9 tube4 7#b7 ,! same rem>k applies to a tube ( l>ge diamet]1 z comp>$ ) "o ( small diamet]1 :atev] ! ?ickness4 7#c7 ,9 ! case ( v l>ge or ?ick tubes ! hot air is advantage\sly employ$ at fir/1 & to complete ! prelim9>y heat+1 ! lum9\s flame alone may be us$4 ,! object ( ?is is to enable ! op]ator to judge1 by ! pres5ce ( soot1 its inability to deposit--or its burn+ (f if deposit$--( ! temp]ature ( ! glass1 & ( ! equality ( ?is temp]ature all ov] ! surface1 = a l>ge & ?ick tube might be heat$ q en\gh to enable x to be safely expos$ to ! full heat be=e x is appreciably yield+ to ! f+]s4 ,9 g5]al1 :5 ! soot burns (f freely1 or lead glass beg9s to %[ ! fa9te/ sign ( r$uction1 or soda glass beg9s to col\r ! flame1 x is m ?an safe to proce$4 ,9 ord] to turn on ! full flame ! op]ator w =m a habit ( hold+ ! "w 9 ! left h& only1 & he w also take c>e n to let any?+ 8 "r h& may be do+ cause him to /op rotat+ ! tube ) 8 left ?umb & f+]4 ,! prelim9>y adju/m5t ( air or oxyg5 supply w enable ! *ange to a flame ( maximum p[] to be made v quickly4 ,! tube hav+ be5 introduc$ ) con/ant rotation1 x w soon s(t5 suffici5tly to be work$4 ,! beg9n] w f9d x be/ to decide ! conv5i5t degree ( s(tness by trial4 ,) soda glass x does n mu* matt] h[ s(t ! glass becomes1 = x rema9s visc\s1 b ) lead glass ! viscosity p]si/s = a long] "t & !n sudd5ly gives place to a mu* great] degree ( fluidity4 ,footnote3 ,?is is only drawn f my impressions acquir$ 9 glass-work+4 ,i h nev] explicitly te/$ ! matt] exp]im5tally4 ,x is j at ?is po9t t a beg9n] w probably meet ) 8 fir/ difficulty4 ,z soon z ! glass gets s(t he w f9d t he no long] rotates ! glass at ! same spe$ by ! "r & left h&1 &1 moreov]1 he w probably unconsci\sly b5d ! tube1 & ev5 de=m x1 by pu%+ or pull+4 ,! second ?ird ( ! art ( ! glass-bl[] consi/s 9 be+ able to move bo? h&s ab\t1 rotat+ a tube ) ea* ?umb & f+]1 & keep+ ! di/ance betwe5 ! h&s1 & also ! spe$ ( rotation1 con/ant4 ,no?+ b long practice c give ?is facility1 b x is ess5tial t x be acquir$ to "s ext5t1 or no progress c be made4 ,"s p acquire a mod]ate pr(ici5cy v quickly1 o!rs1 ( :om ! writ] is "o1 only become reasonably pr(ici5t by mon?s1 or ev5 ye>s1 ( practice4 ,suppos+ t ! tube is n[ ready to be drawn d[n1 ! op]ator w remove x f ! flame1 & w g5tly pull ! ends ap>t1 int]rupt+ 8 turn+ z little z possible4 ,if ! tube be pull$ too h>d1 or if ! area heat$ be too small 7ab\t ?ree-eigh?s ( an in* 9 l5g? 9 ! case giv5 w\ld be prop]71 x w be f\nd t ! ends ( ! two portions ( ! tube w be ne>ly clos$ at a v %>p angle 7ne>ly a "r angle to ! l5g? ( ! tube71 t ! ends w be ?91 & t a long l5g? ( v f9e tube w be produc$4 ,to heat a %ort l5g? ( tube & pull h>d & sudd5ly is ! prop] way to make a v f9e capill>y tube1 b1 9 g5]al1 ?is is :at we want to avoid4 ,if ! op]ation be successfully p]=m$1 ! drawn-d[n tube w h ! appe>ance exhibit$1 :i* is suitable ei!r = subsequ5tly clos+ or h&l+ by means ( ! drawn-d[n portion4 ,! /raightness ( ! po9t c be obta9$ by a little practice 9 feel+ ! glass :5 ! tube is rotat$ z x cools j be=e x loses its visc\s condition4 ,:5 ! op]ation is c>ri$ out prop]ly ! %\ld] ( ! draw %\ld be p]fectly symmetrical & ( ev5 ?ickness1 & its axis reg>d$ z t ( a cone %\ld lie 9 ! axis ( ! tube produc$4 ,! op]ation %\ld be repeat$ till ! /ud5t f9ds t he c produce ?is result ) c]ta9ty1 & he %\ld n be disc\rag$ if ?is takes sev]al days1 or ev5 weeks4 ,( c\rse1 x is probable t )9 ! fir/ h\r he w succe$ 9 mak+ a tol]able job1 b x is 8 bus9ess to le>n nev] to make any?+ else4 ,fig4 #i4 ,fig4 #aj4 ,diagram ( a fold$ end4 #bj4 ,clos+ & bl[+ out ! ,end ( a ,tube4 ,:5 x is desir$ to close ! end ( a p>ticul> bit ( tube1 ?is is easily done by heat+ ! end1 & at ! same "t heat+ ! end ( a wa/e bit ( tube or rod2 ! ends1 :5 plac$ 9 contact1 /ick toge!r1 & a po9t c be drawn d[n z be=e4 ,footnote3 ,po9t is "h us$ 9 ! te*nical s5se1 i4e4 x is a ?9 tail ( glass produc$ by draw+ d[n a tube4 ,hav+ got a po9t1 x w be f\nd t ! ?9 glass cools en\gh to all[ ( ! po9t be+ h&l$ aft] a few mom5ts4 ,! mo/ conv5i5t way ( r$uc+ ! po9t to a suitable l5g? 7say #a4e in*7 is to fuse x (f 9 ! flame1 b ?is mu/ be done neatly2 if a tail is left x may cause inconv5i5ce by cat*+1 or ev5 pi]c+ ! f+] & break+ (f4 ,! bl[-pipe flame be+ turn$ d[n to a suitable size1 & ! %\ld] ( ! draw hav+ be5 kept w>m mean:ile1 let ! tip ( ! flame imp+e on a po9t :]e ! diamet] is ab\t half t ( ! undrawn tube1 & let ! temp]ature be v high 7,fig4 #aa74 ,! tube is to be incl9$ to ! flame s t ! latt] /rikes ! %\ld] normally1 or ne>ly s4 ,!n1 accord+ to circum/ances1 little or mu* ( ! glass c be remov$ at w by draw+ (f ! tail 7,fig4 #ab71 till1 f9ally1 a small drop ( melt$ glass only1 adh]es to ! end ( ! n[ clos$ tube 7,fig4 #ac74 ,fig4 #aa4 ,fig4 #ab4 ,fig4 #ac4 ,fig4 #ad4 ,:5 ?is is satisfactorily accompli%$1 heat ! extreme end ( ! tube mo/ c>efully & equally1 hold+ x 9 su* a position t ! glass w t5d to fl[ f ! bead back on to ! tube1 i4e4 hold ! clos$ end up to ! flame1 ! tube be+1 say1 at #de degrees to ! horizontal4 ,!n :5 ! temp]ature is su* z to indicate complete s(tness lift ! tube to ! m\?1 /ill hold+ ! tube po9t+ ) its clos$ end a little above ! horizontal1 & bl[ g5tly4 ,a beg9n] almo/ always bl[s too h>d4 ,:at is want$1 ( c\rse1 is a cont9u$ pressure1 to give ! visc\s glass "t to yield gradually1 if x is uni=m2 or else int]mitt5t puffs to enable ! ?9n] p>ts1 if !re are any1 to cool m1 & h5ce become m resi/+ ?an ! ?ick] ones4 ,9 any case a little practice w enable ! op]ator to bl[ out a r\nd & ev5 end--nei!r ?ick] nor ?9n] ?an ! re/ ( ! tube4 #ba4 ,to make a ,weld4 ,to beg9 )1 try on two bits ( glass ( ! same size1 i4e4 cut a sev5-in* l5g? ( glass 9 half by scrat*+ x ) ! knife1 & pull+ ! ends ap>t ) a slight incl9ation away f ! scrat*4 ,9 o!r words1 comb9e a small b5d+ mom5t ) a consid]able t5sional /ress4 ,x is important to le>n to d ?is prop]ly4 ,if ! proportions are n well obs]v$1 ! tube w break ) difficulty1 & ! section w n be p]p5dicul> to ! ma9 l5g?4 ,if ! knife is 9 good ord] x w make a f9e deep scrat*--! feel ( ! glass "u ! knife w enable ! op]ator to decide :5 ! scrat* is made4 ,! op]ation ( cutt+ l>ge tubes w be treat$ fur!r on4 ,! two halves ( ! tube be+ held "o 9 ea* h&1 & "o tube clos$ at "o end1 ! extremities to be unit$ w be w>m$1 & !n put 9 ! flame z be=e4 ,fig4 #af4 ,!re are _m ways ( proce$+--p]haps ! easie/ is z foll[s4 ,z soon z ! glass %[s signs ( melt+ at ! ends--& c>e %\ld be tak5 t mu* m is n heat$--take bo? bits out ( ! flame4 ,/op rotat+ = a mom5t1 & re/+ ! arms c>efully on ! edge ( ! table1 raise ! tubes above ! flame & br+ ! ends swiftly & accurately toge!r4 ,?is is a case ( sudd5 dea? no second attempt at mak+ ! ends meet c be all[$2 if ! tubes jo9 9 any o!r ?an a p]fectly exact mann] a k9k m or less objectionable w result4 ,9 practice ! op]ator w le>n to br+ ! ends toge!r1 comm5c+ at "o po9t2 i4e4 ! axes ( ! tubes w be incl9$ at fir/1 s z to cause adh]5ce at "o spot only4 ,if ?is is n q fair1 !n less damage is done 9 mov+ "o tube slightly up or d[n to get ! contact exact4 ,! tubes w !n be clos$ ^u "o ano!r z if !y 7 h+$ at ! jo9t4 ,?is mu/ be done lightly1 yet suffici5tly1 to ensure t ! glass is actually 9 contact all r\nd4 ,hav+ gone s f>1 replace ! tubes--n[ "o--9 ! flame1 & c>efully rotat+ ! glass1 raise ! temp]ature high] ?an 9 ! op]ation j describ$1 9 fact ! high] ! temp]ature1 %ort ( burn+ ! glass1 ! bett]4 ,take ! tube out ( ! flame & bl[ into ! op5 end1 turn+ con/antly z be=e4 ,"o puff is en\gh4 ,!n turn & pull ! glass ap>t till x is ( ! same diamet] & ?ickness ?r\gh\t1 & feel t x is /raight z be=e4 ,?\gh x is 9 g5]al ( high importance t ! jo9t %\ld be well heat$1 ! beg9n] w probably f9d t he ties up 8 glass z soon z x gets really s(t4 ,if 8 object is to make "o jo9t--at any co/--!n let him be c>eful to use two bits ( exactly ! same k9d ( glass1 & only get ! temp]ature up to ! visc\s /age4 ,if ! jo9t be !n pull$ out till x is comp>atively ?91 x w probably /& 7if ( soda glass72 c]ta9ly1 if ( lead glass1 ?\gh 9 ?is case x may n be s\nd4 ,9 any case ! jo9t %\ld be anneal$ 9 ! asbe/os box if practicable1 o!rwise 7unless betwe5 n>r[ tubes7 ) ! asbe/os rag4 ,c>e mu/ be tak5 t ! asbe/os is dry4 #bb4 ,to weld two ,tubes ( diff]5t ,sizes4 ,to d ?is1 ! diamet] ( ! l>g] tube mu/ be r$uc$ to t ( ! small]4 ,! g5]al proc$ure describ$ 9 draw+ d[n mu/ be foll[$1 ) ! foll[+ modification4 ,9 g5]al1 a great] l5g? ( ! tube mu/ be heat$1 & x mu/ be made hott]4 ,! tube is to be gradually drawn 9 ! flame ) con/ant turn+ till ! prop] diamet] & ?ickness ( glass are atta9$4 ,fig4 #af4 ,= ?is op]ation "t mu/ be all[$ if ! op]ator's h&s are /eady en\gh to p]mit ( x2 ! %\ld] %\ld =m p>tly by ! glass s9k+ 9 & p>tly by ! process ( draw+ ! hot glass out4 ,a %\ld] prop]ly prep>$ is %[n 9 ! sket*4 ,beg9n]s g5]ally make ! neck too ?9 on l>ge tubes1 & too ?ick on small] ones4 ,!re ought to be no great diff]5ce 9 ?ickness ( glass betwe5 ! neck on ! l>g] tube1 & ! small] tube4 ,! diamet]s %\ld be z ne>ly z possible alike4 ,hav+ drawn d[n ! l>g] tube to a neck1 take x out ( ! flame1 & z x cools pull & turn till ! neck is ( ! "r ?ickness & is p]fectly /raight1 i4e4 make ! f9al adju/m5t outside ! flame1 & to t end h ! neck r too ?ick 7z to glass7 be=e x is tak5 out4 ,x is n necess>y to wait till ! neck gets cold be=e ! end c be cut (f4 ,make a scrat* z be=e--?is w probably slightly damage ! temp] ( ! file knife1 b t mu/ be put up )4 ,hold ! tube aga9/ ! edge ( ! table1 s t ! scrat* is j above ! level ( ! rim1 & /rike ! upp] "p a sm>t bl[ ) ! h&le ( ! glass knife r 9 ! direction ( its l5g?4 ,footnote3 ,a bit ( hoop iron nail$ aga9/ ! side ( ! table is a v conv5i5t arrangem5t1 & x ne$ n project appreciably above ! g5]al level ( ! rim4 ,( c\rse ?is applies to a tube :]e economy has be5 ex]cis$ & ! end is %ort4 ,if ! tail is long en\gh to =m a h&le1 ! tube may be pull$ ap>t z be=e4 ,z a rule a tempor>y jo9t betwe5 a tube & a rod is n /rong en\gh to enable ! %\ld] to be brok5 at ! scrat* by m]e pull+4 ,! ends to be weld$ mu/ be brok5 (f v clean & true4 ,subsequ5t op]ations are to be c>ri$ out z already describ$4 #bc4 ,! above op]ations w be easily p]=m$ on tubes up to half an in* 9 diamet]1 if !y are n too long4 ,x is ! l5g? ( tube1 & consequ5t difficulty 9 giv+ id5tity ( motion ) ! two h&s1 :i* make ! jo9t+ ( long tubes difficult4 ,!re are also difficulties if ! tubes are v ?91 h a v f9e bore or a v l>ge diamet]4 ,all ^! difficulties m]ely amuse a good glass-bl[]1 b to an exp]im5t] :o wants to get on to o!r ?+s be=e suffici5t skill is acquir$ 79 ! movem5t ( ! h&s & arms7 ! foll[+ me?od is recomm5d$4 ,fir/1 use fl9t glass4 ,!n1 assum+ t any draw+ d[n has to be done1 d x z well z possible1 = on ?is ! success ( ! me?od to be describ$ especially dep5ds4 ,be sure t ! tubes to be weld$ are cut (f clean & are z ne>ly z may be ( ! same size at ! po9t ( junction4 ,to fix ! description1 suppose x is desir$ to jo9 two tubes 7see ,fig4 #h71 ea* ab\t "o in* 9 diamet] & a y>d long4 ,get f\r clip /&s & place !m on a level table4 ,be sure t ! /&s are firm & h n w>p$ s z to rock4 ,9 ea* pair ( clips place a tube1 s t ! two tubes are at ! same height f ! table1 &1 9 fact1 exactly abut1 ) axes 9 ! same /raight l9e4 ,close "o tube by a cork & !n fix ! bl[+ app>atus z %[n to ! o!r4 ,9 su* an op]ation z ?is ! dry+ app>atus may be disp5s$ )1 & a rubb] tube simply connect$ to "o end ( ! sy/em & br\ght to ! m\?4 ,take ! oxyg5 bl[-pipe & turn ! nozzle till ! flame issues t[>ds y1 & see t ! flame is 9 ord]4 ,!n turn d[n ! oxyg5 till x only suffices to cle> ! smoky flame1 & comm5ce to heat ! propos$ jo9t by a curr5t ( hot air1 mov+ ! flame r\nd ! jo9t4 ,f9ally1 br+ to be> ! mo/ p[]ful flame y c get out ( ! bl[-pipe1 & c>ry x r\nd ! jo9t s quickly t y h ! latt] all hot at once4 ,put d[n ! bl[-pipe1 &1 us+ bo? h&s1 press ! tubes toge!r 7:i* wood5 clips w readily all[71 & aft] see+ t ! glass has t\*$ ev]y:]e1 pull ! tubes a trifle ap>t4 ,apply ! bl[-pipe aga91 pass+ lightly ov] ! ?9 p>ts1 if any1 & heat+ ?ick] ones2 hav+ ! end ( ! rubb] tube 9 8 m\?1 ! op]ator w be able to bl[ out ?ick places4 ,:5 all is hot1 bl[ out slightly1 & hav+ tak5 ! flame away1 pull ! tubes a little ap>t1 & see t !y are /raight4 ,?r[ an asbe/os rag ov] ! jo9t1 loos5 "o pair ( ! clamps slightly1 & leave ! jo9t to anneal4 ,x is important t ! lea/ possible am\nt ( glass %\ld be heat$1 h5ce ! necessity ( hav+ ! ends well prep>$1 & x is also important t ! "w %\ld be done quickly2 o!rwise glass w fl[ f ! upp] side d[nw>ds & no /rong jo9t w be obta9$4 ,fig4 #ag4 ,tube be+ op5$ at "o end4 #bd4 ,to weld ,tubes ( v small ,bore4 ,if ! bore is n s small z to prev5t ! entrance ( ! po9t ( ! iron nail1 get ! ends ( ! tubes hot1 & op5 ! bore by ins]t+ ! end ( ! nail previ\sly sme>$ ov] ) a trace ( vasel9e4 ,"w ! nail r\nd by hold+ ! h&le betwe5 ! ?umb & fir/ f+] ( ! "r h&1 ! tube be+ simil>ly plac$ 9 ! left4 ,! tube & nail %\ld be incl9$ z %[n 9 ! sket*4 ,nev] try to =ce ! op]ation2 ! nail soon cools ! glass1 s t only a v %ort "t is available aft] ea* heat2 dur+ ?is ! tube %\ld be rotat$ aga9/ ! nail r ?an ! nail aga9/ ! tube4 ,be c>eful n to heat a great] l5g? ( tube ?an is necess>y1 or ! nail w1 by its compon5t ( pressure along ! tube1 cause ! latt] to jump up or ?ick5 & bulge4 ,bo? ends be+ prep>$1 & if possible1 kept hot1 ! weld may be made z be=e1 & ! heat+ cont9u$ till ! glass falls 9 to ab\t its previ\s ?ickness1 leav+ a bore only slightly great] ?an be=e4 ,x is 9 op]ations su* z ?is t ! asbe/os box w be f\nd ( great use4 ,z soon z "o end ( ! weld is ready cool x 9 ! flame till soot deposits1 & !n plunge x into ! asbe/os4 ,?is w cause x to cool v sl[ly1 & r5d]s x less likely to crack :5 aga9 br\ght into ! flame4 ,turn$-out ends1 if ! glass is at all ?ick1 are v liable to crack (f on reheat+1 s t !y mu/ be re9troduc$ 7into ! flame7 ) especial c>e4 ,?is liability to breakage is r$uc$1 b n elim9at$1 by ! asbe/os anneal+4 ,figs4 #ah & #ai4 #be4 ,:5 ! bore is v f9e1 x is be/ to seal (f ! tubes1 & bl[ an incipi5t bulb ne> "o end ( ea* tube4 ,^! bulbs may be cool$ 9 asbe/os1 & cut across :5 cold by means ( a scrat* t\*$ at "o end 7,figs4 #ah & #ai7 by a f9e po9t ( highly inc&esc5t glass4 ,= details ( ?is me?od see p4 #df1 ,fig4 #ba4 ,"t is occasionally sav$ by bl[+ (f ! ends ( ! bulbs4 ,! details ( ?is process w be describ$ :5 ! op]ation ( mak+ ?i/le-head$ tubes is dealt )4 #bf4 ,:5 ! tubes are bo? ( l>ge diamet]1 long1 & v ?9 7cyl9d] tubes71 a consid]able am\nt ( difficulty w be exp]i5c$4 ,on ! :ole1 x is be/ to heat ea* end sep>ately till ! glass ?ick5s a little1 anneal 9 ! flame & 9 asbe/os1 & !n proce$ z 9 #bb4 ,if ! ends are n q true1 x w be f\nd t q a ?ickness ( glass may be jump$ toge!r at "o side ( ! tubes1 :ile ! edges are /ill ap>t at ! o!r4 ,:5 ?is looks likely to happ51 incl9e ! tubes z if ! jo9t 7 a h+e1 & b5d back quickly2 d n simply cont9ue to pu% ! tubes toge!r 9 a /raight l9e1 or an unmanageable lump ( glass w be =m$ on "o side4 ,if 9 spite ( ^! precautions su* a lump does =m1 proce$ z foll[s4 ,take a rod ( glass1 at lea/ "o-eigh? ( an in* ?ick1 & w>m x 9 ! flame at "o end4 ,heat ! imp]fect jo9t till x s(t5s all r\nd1 & !n br+ ! flame "r up to ! ?ick "p1 & heat t z rapidly & locally z possible4 ,! oxygas flame does ?is magnific5tly4 ,press ! heat$ end ( ! glass rod aga9/ ! ?ick "p1 & pull (f z mu* ( ! lump z x is desir$ to remove1 aft]w>ds bl[+ ! d9t out by a judici\s puff4 ,f9i% (f z be=e4 #bg4 ,occasionally1 :5 x is se5 t 9 ord] to produce a jo9t clos$ all r\nd1 "o side ( ! tube w\ld be too mu* ?ick5$1 x is bett] to pat* ! op5 side4 ,= ?is purpose take a glass rod ab\t "o-sixte5? in* 9 diamet]1 & turn ! flame to give its greate/ effect1 /ill keep+ r an excess ( air or oxyg54 ,see t ! side ( ! jo9t already made is kept fairly hot--x ne$ n be s(t2 int]rupt any o!r "w (t5 en\gh to ensure ?is4 ,!n1 direct+ ! flame *iefly on ! ?9 rod1 beg9 to melt & pull ! glass ov] ! edges ( ! gap4 ,:5 ! gap is clos$ get ! lump v hot1 s t all ! glass is well melt$ toge!r1 & !n1 if necess>y1 pull ! excess ( glass (f1 z be=e describ$4 ,x mu/ be rememb]$ t ?is & ! me?od ( ! previ\s section are em]g5cy me?ods1 & nev] give su* nice jo9ts z a manipulation :i* avoids !m1 i4e4 :5 ! ends ( ! tubes are p]fectly /raight & true to beg9 )4 ,also note t1 z ! tubes _c be kept 9 rotation :ile be+ pat*$1 x is z well to "w at z l[ a temp]ature z possible1 consi/5tly ) ! o!r conditions1 or ! glass w t5d to run d[n & =m a drop1 leav+ a correspond+ly ?9 place beh9d4 ,fig4 #bj4 #bh4 ,a v common fault 9 cutt+ a tube ( ab\t an in* 9 diamet] is to leave x ) a project+ po9t1 z %[n4 ,?is c be sl[ly *ipp$ (f by ! pli]s1 us+ ! jaws to cru% & gr9d away ! edge ( ! projection2 x is fatal to attempt to break (f l>ge pieces ( glass all at once4 #bi4 ,x w be conv5i5t "h to m5tion "s me?ods ( cutt+ l>ge tubes4 ,) tubes up to an in* & a half 9 diamet]1 & ev5 ov] ?is--provid$ t ! glass is n v ?ick--we may proce$ z foll[s3 ,make a good scrat* ab\t half an in* long1 & pretty deep1 i4e4 pass ! knife backw>ds & =w>ds two or ?ree times4 ,press a po9t ( melt$ glass exactly on "o end ( ! scrat*2 ! glass po9t ev5 :5 press$ out ( %ape %\ld n be z l>ge z a button "o-twelf? ( an in* 9 diamet]4 ,if ?is fails at fir/1 repeat ! op]ation two or ?ree times4 ,fig4 #ba4 ,if a crack does n =m1 t\* ! hot place ) ! cold end ( ! nail4 ,if no success is obta9$1 try ! o!r end ( ! scrat*4 ,if failure /ill pursues ! op]ator1 let him make ano!r cut on ! opposite side ( ! tube & try aga94 ,9 g5]al1 ! tube w yield ! fir/ or second "t ! hot drop ( glass is appli$4 ,nev] apply ! drop at ! c5tre ( ! scrat*1 or a ragg$ crack1 :i* may run 9 any direction1 w result4 ,v (t51 ) a l>ge tube1 ! crack =m$ by a successful op]ation w only ext5d a %ort di/ance4 ,9 ?is case x is desirable to entice ! crack r\nd ! tube1 & n tru/ to its runn+ /raight :5 ! tube is pull$ ap>t4 ,on ! :ole1 ! be/ me?od 9 ?is case is to employ a flame p5cil1 :i* %\ld be kept ready = use4 ,?is m]ely consi/s ( a bit ( glass tube ( ab\t ! same dim5sions z an ord9>y lead p5cil1 drawn d[n to a v f9e jet at "o end4 ,! jet mu/ n be v long or ?91 or ! glass w soon fuse up4 ,a few trials w enable ! op]ator to get ! prop] proportions1 :i* are su* t ! tube has ! g5]al appe>ance ( a p5cil normally %>p5$ 7say ) a cone ( #fj'74 ,?is tube is be/ made ( h>d glass4 ,connect x to a gas supply by light flexible tub+1 & turn d[n ! gas till ! flame f ! end ( ! jet is n m ?an "o-t5? ( an in* long4 ,!n apply ! jet1 beg9n+ f ! end ( ! crack1 & gradually draw x 7! crack7 r\nd ! tube4 ,! op]ation w be assi/$ if a rubb] r+ is slipp$ on ! tube to beg9 )1 s t ! eye has "s guide z to :e!r ! flame is be+ drawn r\nd prop]ly or n4 ,! r+ mu/1 ( c\rse1 be f> en\gh away to escape ! effect ( ! flame4 ,! crack w be f\nd to foll[ ! flame 9 ! mo/ docile mann]1 unless ! tube is ?ick or badly anneal$4 ,"s op]ators recomm5d a p5cil ( gl[+ *>coal1 b ! flame is und\bt$ly bett]4 #cj4 ,to cut v ?ick ,tubes4 ,a l>ge numb] ( me?ods h be5 propos$1 & ne>ly ev]ybody has 8 fav\rite4 ,! foll[+ has always succe$$ ) me4 ,fir/ m>k on ! tube1 by means ( a little dead black _s pa9t1 exactly :]e ! cut is to be4 ,!n %>p5 ! glass knife & scrat* a q deep cut all r\nd3 !re is no difficulty 9 mak+ ! cut "o-tw5tie? ( an in* deep4 ,x w be prop] to lubricate ! knife ) k]os5e aft] ! fir/ m>k is made4 ,footnote3 ,! edge ( ! knife may be advantage\sly sav$ by us+ an old file moi/5$ ) k]os5e = ! purpose4 ,i f9d k]os5e is n worse1 b1 if any?+1 bett] ?an ! solution ( camphor 9 turp5t9e recomm5d$ by ,mr4 ,%5/one4 ,if ! glass is ab\t "o-eigh? ( an in* ?ick1 ! scrat* maybe conv5i5tly ab\t "o-tw5tie? ( an in* deep1 b if ! glass is any?+ l "o-qu>t] ( an in* ?ick1 ! scrat* mu/ be mu* deep]1 9 fact1 ! glass may be half cut ?r\gh4 ,to make a v deep scrat*1 a :eel arm$ ) diamond du/1 :i* w be describ$ lat] on1 may be us$4 ,h[ev]1 x is n ess5tial to use a diamond :eel1 ?\gh x saves "t4 ,:5 ! cut is made to a suffici5t dep? proce$ ?us3 ,obta9 two /rips ( bibul\s pap] or bits ( tape & twi/ !m r\nd ! tube on ea* side ( ! scrat*1 all[+ n m ?an "o-eigh? ( an in* betwe5 !m4 ,!n add a few drops ( wat] to ea*1 till x is ?or\ghly soak$1 b n all[+ wat] to run away4 ,dry out ! scrat* by a %r$ ( blott+ pap]4 ,turn d[n ! oxygas flame to ! smalle/ dim5sions1 & !n boldly apply x ) its hotte/ "p play+ "r into ! nick & at a s+le po9t4 ,probably 9 ab\t two seconds1 or less1 ! tube w break4 ,if x does n1 rotate ! tube1 b /ill s t ! flame plays 9 ! nick4 ,aft] mak+ ! tube v hot all r\nd--if x has n brok5--apply ! flame aga9 /eadily at "o po9t = a few seconds & !n apply a bit ( cold iron4 ,if ! tube does n break at once dur+ ^! processes1 let x cool1 & cut ! groove deep]2 !n try aga94 ,footnote3 ,?is me?od is cont9ually be+ re9v5t$ & publi%$ 9 ! v>i\s j\rnals4 ,x is ( unkn[n antiquity4 ,fig4 #bb4 ,if ! tube breaks aft] great heat+ & long ef=ts1 x w probably leave incipi5t cracks runn+ away f ! break1 or may ev5 break irregul>ly4 ,a good break is ne>ly always "o t 0 easily made4 ,if a numb] ( r+s h to be cut1 or a numb] ( cuts made on glass tubes ( ab\t ! same size1 x w be f\nd economical 9 ! end to m\nt a glazi]'s diamond = ! purpose4 ,a simple b suitable app>atus is figur$ 7,fig4 #bc74 ,fig4 #bc4 ,! only difficulty is to regulate ! position ( ! diamond s t x cuts4 ,9 ord] to d ?is1 c>efully note its cutt+ angle by prelim9>y trials on %eet glass1 & !n adju/ ! diamond by clamps1 or by wriggl+ x 9 a =k1 z %[n4 ,weight ! bo>d v slightly1 s z to give ! small necess>y pressure1 & produce ! cut by rotat+ ! tube by h&4 ,:5 a cut is ne>ly complet$ take great c>e t ! two ends jo91 or irregul>ity w result4 ,?is is n always easy to d unless ! tube happ5s to be /raight4 ,hav+ got a cut1 />t a crack by means ( a f9e light wat*mak]'s hamm]1 or ev5 a bit ( fus$ glass1 & entice ! crack r\nd ! cut by tapp+ ) ! hamm] or by means ( ! flame p5cil4 ,if ! cut is a true cut ! tube w break at once4 ,z a supply ( electrical curr5t = light+ w1 9 ! ne> future1 be z mu* a matt] ( c\rse = laboratory purposes z a gas supply1 ,i add ! foll[+ note4 ,to heat a tube r\nd a scrat*1 no?+--n ev5 ! oxygas bl[-pipe--is s good z a bit ( plat9um or iron wire electrically heat$4 ,if ! crack does n />t by consid]able heat+ ( ! glass1 /op ! curr5t1 unw9d ! wire1 & t\* ! glass on ! crack ei!r ) a bit ( cold copp] wire or a wet mat* /em4 ,i pref] ! copp] wire1 = 9 my exp]i5ce ! wat] w occasionally produce an explosion ( cracks4 ,on ! o!r h&1 ! cold wire frequ5tly fails to />t a crack4 ,judg+ f ! appe>ance ( ?ick tubes z suppli$ by ! deal]s1 ! factory me?od ( cutt+ (f appe>s to be to gr9d a nick almo/ ?r\gh ! tube1 & "r r\nd2 & = really ?ick glass ?is is ! safe/ b sl[e/ way2 a ?9 em]y :eel kept wet w d ?is p]fectly4 ,suitable :eels may be pur*as$ f ! ,norton ,em]y ,:eel ,co4 ( ,b$=d1 ,mass1 ,u4,s4,a4--9 ,engl& ?r\gh ,messrs4 ,*ur*ill & ,co4 ( ,london1 import]s4 #ca4 ,to bl[ a ,bulb at ! ,end ( a ,tube4 ,i mu/ admit at once t ?is is a difficult op]ation--at all ev5ts1 if a l>ge bulb is requir$4 ,h[ev]1 all !re is to be said c be said 9 few words4 ,9 g5]al1 :5 a bulb is requir$ at ! end ( a tube x w be necess>y to ?ick5 up ! glass4 ,a pr(essional glass-work] w g5]ally accompli% ?is by jump+ up ! tube1 i4e4 by heat+ x :]e ! bulb is requir$1 & compress+ x little by little until a suffici5t am\nt ( glass is collect$4 ,! amateur w probably f9d t he gets a v irregul> mass 9 ?is way1 & w be tempt$ to beg9 by weld+ on a %ort bit ( wide & ?ick tub+ prep>atory to bl[+ out ! bulb4 ,h[ev]1 suppos+ t en\gh glass is assembl$ by-ei!r ( ^! me?ods1 & t x is q uni=m 9 ?ickness1 let ! ?ick5$ "p be heat$ along a circle till x becomes mod]ately s(t1 & let x !n be exp&$ ab\t "o-fif?1 say by g5tly bl[+4 ,x is p]haps m important to keep turn+ ! glass dur+ bulb-bl[+ ?an 9 any o!r op]ation1 & ?is bo? :5 ! glass is 9 ! flame & :ile ! bulb is be+ bl[n4 ,x is also v important to avoid draughts4 ,9 g5]al1 a bulb is be/ bl[n ) ! tube 9 a ne>ly horizontal position1 b slop+ slightly upw>ds f ! m\?4 ,if x be notic$ t a bulb t5ds to bl[ out m at "o side ?an ano!r1 let ! side ( greate/ protub]ance be turn$ d[n1 s t x is at ! l[e/ po9t1 r$uce ! pressure = an in/ant1 & !n bl[ aga94 ,x w be obs]v$ t ! bulb w n[ exp& at ! top4 ,! reason ( ?is is *iefly t ! "u side cools mo/ rapidly 7accord+ to ,f>aday1 ,*emical ,manipulation1 #aaid71 & consequ5tly c exp& no fur!r2 b also x is n unlikely t ! glass t5ds to fl[ some:at f ! upp] side1 :i* rema9s hot1 & consequ5tly ! bulb1 :5 ! next puff rea*es x1 w t5d to yield at ?is po9t4 ,by heat+ sev]al zones ! tube w become gradually exp&$4 ,fig4 #bd4 ,fig4 #be4 ,fig4 #bf4 ,:5 ! l5g? ( ! ?ick5$ "p ( ! tube only slightly exce$s its diamet] 7,fig4 #be71 let ! :ole be br\ght to a temp]ature :i*1 ) fl9t glass1 %\ld be j %ort ( t ( p]fect fluidity2 & !n1 hold+ ! tube horizontally & con/antly turn+ x1 let ! bulb be bl[n out to its full size1 not+ ! appe>ances & correct+ too great protub]ance on any side by ! means above m5tion$4 ,if ! bulb appe>s pe>-%ap$ turn ! tube s t ! melt$ mass is direct$ upw>ds2 if ! bulb h ! contr>y fault1 correct 9 ! correspond+ mann]4 ,! bulb :5 f9i%$ may be lightly tapp$ on ! table1 :51 if !re is any weak place ow+ to inequality ( ?ickness1 ! bulb w break1 & ! op]ation may be />t$ afre%4 ,a good bulb is r\nd1 set truly on ! tube1 & free f lumps ( ?ick glass or places ( excessive ?9ness4 ,:5 ! amateur has succe$$ 9 bl[+ a bulb two in*es 9 diamet] on ! end ( a /rong bit ( !rmomet] tube--say = an air !rmomet]--he may well seek ! congratulations ( 8 fri5ds4 ,9 case ! bulb is n satisfactory on a fir/ attempt1 x may be melt$ d[n aga91 if ! foll[+ precautions are tak54 ,directly creases beg9 to appe> 9 ! bulb let x be )drawn f ! flame1 & g5tly bl[n till ! creases come out4 ,by alt]nate heat+ & bl[+ ! glass c be got back to its orig9al =m1 or ne>ly s1 b unless ! op]ator %[s great skill & judgm5t1 ! probability is t ! glass w be unev54 ,by heat+ & keep+ ! ?ick] p>ts 9 ! high] position1 & bl[+ a little n[ & aga91 ! glass may be got ev51 & a new attempt may be made4 ,x mu/ n be suppos$ t ?is process c be c>ri$ on indef9itely1 = ! glass t5ds to lose its visc\s prop]ties aft] a "t1 or1 at all ev5ts1 x p]i%es 9 "s way1 especially if x has be5 all[$ to get v ?92 consequ5tly too frequ5t attempts on ! same glass are unpr(itable4 ,two or ?ree trials are z _m z x g5]ally pays to make4 ,z a rule ! l>ge/ possible flame may be us$ ) advantage 9 ?is op]ation4 #cb4 ,to bl[ a bulb 9 ! middle ( a tube1 ! proc$ure is mu* l t already treat$1 b ! manipulation is1 if any?+1 m difficult1 = ! fur!r end ( ! tube mu/ be c>ri$ & turn$ z well z ! end :i* is held to ! lips4 #cc4 ,to make a side ,weld4 ,?is is by no means difficult1 b is easi] ) lead glass ?an ) soda glass4 ,! tube to :i* x is desir$ to make a side connection hav+ be5 select$1 x is clos$ at "o end by rubb] tube /ops1 or 9 any o!r suitable mann]4 ,! zone ( ! propos$ connection is not$1 & ! tube is br\ght to ne> s(tness r\nd t circle 7if ! tube is made actually s(t1 inconv5i5ce w arise f ! b5d+1 :i* is sure to occur74 ,two c\rses are !n op5 to ! op]ator1 "o suitable to a ?ick tube1 ! o!r to a tube ( mod]ate ?ickness4 ,tak+ ! =m] fir/4 ,provide a piece ( glass rod & w>m its end4 ,direct a small flame aga9/ ! spot on ! ?ick tube :]e ! propos$ jo9t is to be4 ,:5 ! glass becomes almo/ inc&esc5t at ?is spot1 put ! end ( ! rod aga9/ x & draw out a ?read ( glass till suffici5t metal has be5 remov$4 ,!n fuse (f ! ?read close to ! tube4 ,fig4 #bg4 ,! subsequ5t proc$ure is ! same z = ?9 tubes4 ,9 ?is case heat ! spot by ! smalle/ flame available1 & get ! spot v hot4 ,bl[ x out g5tly into a bubble1 p]haps ext5d+ to a height equal to its diamet]4 ,!n heat ! top ( ! bubble till x is inc&esc5t & bl[ viol5tly4 ,?is w produce an op5+ fr+$ by glass s ?9 z to exhibit int]f]5ce col\rs4 ,remove ! filmy "p1 & heat ! fray$ edges till !y coh]e & =m an incipi5t tube4 ,if ! flame has be5 ( a correct size1 ! tube w n[ be ( ! same diamet] z ! tube to be weld$ on1 & w project p]haps "o-sixte5? ( an in* f ! surface ( ! ma9 tube 7,fig4 #bh74 ,fig4 #bh4 ,fig4 #bi4 ,:5 ?is /age is rea*$1 aga9 heat ! tube all r\nd till x ne>ly s(t5s1 & by means ( ! o!r h& heat ! end ( ! o!r tube :i* x is propos$ to weld4 ,j be=e ! ma9 tube actually s(t5s1 turn x s z to heat ! edges ( ! ap]ture1 & at ! same "t get ! end ( ! side tube v hot4 ,take bo? out ( ! flame = an in/ant1 & press ! p>ts toge!r1 in/antly slightly )draw+ ! side tube4 ,if ! op]ation is well p]=m$1 x w be f\nd t ! po9t ( maximum ?ickness ( glass is n[ cle> ( ! ma9 tube4 ,! jo9t is !n to be heat$ all r\nd & bl[n out--a r awkw>d op]ation1 & "o requir+ "s practice1 b x c be done4 ,fig4 #cj4 ,if great /r5g? is want$1 heat ! ma9 tube all r\nd ! jo9t bit by bit1 & bl[ ea* section slightly outw>ds4 ,if ! op]ator is confid5t 9 8 skill1 he %\ld !n heat ! :ole jo9t to ! s(t5+ po9t1 bl[ x out slightly1 & !n adju/ by pull+ & pu%+4 ,cool fir/ 9 ! gas flame1 & !n plunge ! jo9t into ! asbe/os & cov] x up--or if too l>ge1 ?r[ ! asbe/os clo? r\nd x4 ,9 ! case ( soda glass ?is f9al g5]al heat is almo/ ess5tial1 b x is n s ) fl9t glass1 & z ! g5]al heat is ! mo/ difficult "p ( ! job1 x w be f\nd easi] to use lead glass & omit ! g5]al heat+4 ,) soda glass a v small irregul>ity w cause ! jo9t to break :5 cold1 b fl9t glass is mu* m long-suff]+4 ,x is easy to p]=m ! above op]ation on small tubes4 ,= l>ge ones x w be f\nd be/ to employ fl9t glass & use ! clip /&s z 9 ! case ( direct welds1 treat$ above1 b1 ( c\rse1 ) suitable modifications4 ,nev] let ! ma9 tube cool aft] ! hole is made until ! "w is done4 #cd4 ,ins]t$ ,jo9ts4 ,9 _m in/ances ! p]=mance ( app>atus is mu* improv$ by jo9ts ( ?is k9d1 ev5 :5 _! use is n absolutely ess5tial4 ,!re are two ways 9 :i* ins]t$ jo9ts may be made4 ,! fir/ me?od is ! easi]1 & works well ) fl9t glass2 b :5 "o comes to apply x to soda glass !re is a dang] ( ! glass becom+ too ?ick ne> ! jo9t1 & ?is (t5 leads to a crack+ ( ! jo9t z ! glass cools4 ,fig4 #ca4 ,suppose x is desir$ to ins]t ! tube ,b into ! tube ,a 7,fig4 #ca74 ,beg9 by r$uc+ ! size ( ! end ( tube ,a till ,b w j slip 9 q easily4 ,) ,b ab\t "o-qu>t] in* 9 diamet]1 a cle>ance ( ab\t "o-tw5tie? ( an in*1 or less1 9 all 7i4e4 "o-=tie? ( an in* on ea* side7 w be prop]4 ,heat ,b by itself at ! propos$ zone ( junction1 & bl[ out a v n>r[ r+2 !n compress ?is slightly s t x =ms an almo/ clos$ r+ ( glass4 ,! figure ref]s to ! close ( ?is op]ation 7,fig4 #ca1 ,b74 ,x does n matt] mu* :e!r ! r+ rema9s a m]e flatt5$ bulb1 or :e!r x is a solid r+1 b x mu/ be "o or ! o!r4 ,"s judgm5t mu/ be ex]cis$ 9 prep>+ ! r+4 ,9 g5]al1 ! beg9n] w collect too mu* glass 9 ! r+1 & consequ5tly ! jo9t1 :5 made1 w ei!r be ?ick & liable to crack easily1 or x w be bl[n out into an erratic %ape 9 endeav\rs to r$uce ?is ?ickness4 ,accord+ly1 ! op]ator w1 if necess>y1 ?9 ! tube ,b by draw+ slightly1 if he consid]s x desirable1 be=e ! little enl>gem5t is bl[n out4 ,9 g5]al1 two heats mu/ be us$ = ?is op]ation4 ,fig4 #cb4 ,get ! approximat+ p>ts ( bo? ,a & ,b up to a temp]ature j bel[ t at :i* !y w adh]e1 & hav+ clos$ ! o!r end ( ,a1 place ,b c>efully )9 x up to ! r+1 & if x c be arrang$1 h a mica wad 9 ,a1 ) a c5tral hole ?r\gh :i* ! end ( ,b c project4 ,?is w v mu* facilitate ! op]ation1 especially if ,b is long1 b may be disp5s$ ) by ! ex]cise ( c>e & skill4 ,! op]ation is n[ simple4 ,fuse ! junction & press ! tubes lightly toge!r1 be+ c>eful n to collect m glass ?an c be help$2 f9ally1 bl[ out ! jo9t & r$uce ! ?ickness by mild draw+ 7,fig4 #cc74 ,9 ord] to make a really good jo9t1 two po9ts mu/ be p>ticul>ly att5d$ to--! rim mu/ be ?9 & its plane p]fectly p]p5dicul> to ! axis ( tube ,b2 ! end ( tube ,a mu/ be cut (f q clean & p]p5dicul> to its axis be=e ,b is ins]t$4 ,s important are ^! conditions--especially ! latt] t ! writ] has ev5 occasionally us$ ! gr9d/one to get ! end ( ,a into a prop] condition1 an admission :i* w probably e>n ! contempt ( ! exp]t glass-work]4 ,fig4 #cc4 ,n[ = ! second me?od1 :i* is (t5 practis$ 9 ,g]many1 :]e soda glass is *iefly us$4 ,) ?is glass ! *ief po9t is to get a v ev5 & n too ?ick r+ at ! junction1 & consequ5tly ! extra ?ick5+ produc$ by mak+ a rim on ,b is r a drawback4 ,! me?od consi/s 9 cutt+ (f f ,b ! l5g? :i* x is desir$ to ins]t1 slipp+ ?is into ,a 7:i* may be an o!rwise clos$ bulb1 = in/ance71 & !n gradually melt+ up ! op5 end ( ,a till ! piece ( ,b inside w no long] fall out4 ,by hold+ ! jo9t d[nw>ds s t ! ins]t$ portion ( ,b re/s on ! edges ( ! op5+1 a jo9t may be made ) ! m9imum ?ick5+4 ,! ext]nal "p ( ,b1 previ\sly heat$1 is !n appli$1 & ! jo9t subject$ to a g5]al heat & bl[n out4 ,v nice jo9ts may be made by ?is me?od1 & x is p]haps ! bett] "o :]e ! ext]nal "p ( ,b is to be less 9 diamet] ?an ! ins]t$ "p4 ,x 0 9 ?is mann] t ! writ] 0 taught to make glass velocity pumps1 "o ( :i*1 ( a good design1 is figur$ z an example4 ,9 all cases good anneal+ %\ld foll[ ?is op]ation4 ,if ! ins]t$ "p ( ! inn] tube 7,b7 is any?+ l an in* 9 diamet]1 & especially if x is ( any l5g?1 z 9 "s =ms ( ozone app>atus1 or 9 a l>ge ,buns5's ice calorimet]1 ! arrangem5ts = support+ ! inn] "p mu/ be v good4 ,a conv5i5t way ( proce$+ :5 ! inn] tube is well support$ is to make ! m\? ( ,a only v little l>g] ?an ! diamet] ( ,b1 s t ,b w only j slip 94 ,!n ! m\? ( ,a & ! zone ( ,b may be heat$ toge!r1 & ,b bl[n out ^u ,a4 ,?is1 ( c\rse1 mu/ be arrang$ =1 if necess>y1 by tempor>ily /opp+ ! inn] end ( ,b4 ,! inn] support ( ,b %\ld be remov$ z soon z practicable aft] ! jo9t is made1 or1 at all ev5ts1 %\ld n be p]fectly rigid2 a tightly-fitt+ cork1 = in/ance1 is too rigid4 ,! reason is1 ( c\rse1 t 9 cool+ !re may be a t5d5cy to set ,b a little to "o side or ! o!r1 & if x is n free to take su* a set1 ! jo9t mo/ probably w give way4 ,good anneal+ bo? ) flame & asbe/os is a s9e qua non 9 all ins]t$ "w4 ,fig4 #cd4 #ce4 ,b5d+ ,tubes4 ,i h hi!rto said no?+ ab\t b5d+ tubes1 = to b5d a tube ( a qu>t] ( an in* 9 diamet]1 & ( ord9>y ?ickness1 is ab\t ! fir/ ?+ "o le>ns 9 any laboratory1 :ile to b5d l>ge tubes nicely is z difficult an op]ation z ! practice ( glass-bl[+ af=ds4 ,h[ev]1 ev5 9 b5d+ a n>r[ tube x is possible to proce$ 9 ! wrong way4 ,! wrong way is to heat a %ort l5g? ( ! tube & !n b5d x rapidly1 hold+ ! plane ( ! b5d horizontal4 ,! "r way1 p] contra1 is to use a batsw+ burn] to heat1 say1 two in*es ( ! tube ) con/ant turn+ till x is v s(t1 & !n1 hold+ ! glass s t ! b5d w be 9 a v]tical plane pass+ ?r\gh "o eye 7! o!r be+ %ut71 to make ! b5d r sl[ly4 ,if an exact angle is requir$1 x is z well to h x drawn out on a %eet ( asbe/os bo>d4 ,9 ?is case b5d ! glass z describ$ till x is approximately "r1 & f9i% by lay+ x on ! asbe/os bo>d & br++ x up to ! m>ks4 ,a suitable bit ( wood may be sub/itut$ = ! asbe/os on occasion4 ,n4,b3 ,! laboratory table is n a suitable piece ( wood4 ,a "r-angl$ b5d is (t5 want$4 ,9 ?is case ! corn] ( a table w s]ve z a good guide to ! eye1 ! glass be+ f9i%$ by be+ held j above x4 ,if great accuracy is want$1 make a wood5 template & susp5d x by a screw f ! side ( ! table1 s t ! v]tex ( ! gauge = ! int]ior angle projects d[nw>ds1 !n f9i% by b5d+ ! tube r\nd x4 ,! wood may be ab\t half an in* ?ick4 ,if a %>p b5d is requir$1 heat ! tube 9 ! bl[-pipe1 & b5d x rapidly1 bl[+ out ! glass mean:ile4 ,! reason :y a long b5d %\ld be held 9 a v]tical plane is t ! hot "p t5ds to droop out ( ! plane ( ! b5d if ! latt] be made 9 a horizontal position4 ,to b5d a tube above half an in* 9 diamet] is a m or less difficult op]ation1 & "o :i* increases 9 difficulty z ! diamet] ( ! tube increases4 ,a ,u-tube1 = in/ance1 may be made z foll[s3 ,use ! f\r bl[-pipe arrangem5t s z to heat a fair l5g? ( tube1 & get1 say1 two in*es ( tube v hot--almo/ fluid1 9 fact--by means ( ! c>bon block support$ f a /&4 ,remove ! tube rapidly f ! flame & draw ! hot "p out to1 say1 ?ree in*es4 ,!n1 hold+ ! tube s z to make ! b5d 9 a v]tical plane1 b5d x & bl[ x out toge!r to its prop] size4 ,?is op]ation seems to pres5t no difficulties to exp]i5c$ glass-work]s1 ev5 ) tubes ( ab\t "o in* 9 diamet]1 b to ! amateur x is v difficult4 ,i always look on a l>ge ,u-tube ) feel+s ( envy & admiration1 :i* ! complex trick "w ( an elaborate vacuum tube does n excite 9 ! lea/4 ,x w be not$ t ?is me?od may1 & (t5 does1 involve a prelim9>y ?ick5+ ( ! glass4 ,) tubes ov] an in* 9 diamet] ,i h no idea z to :at is ! be/ mode ( proc$ure--:e!r1 = in/ance1 a quantity ( s& or gas coke might n be us$ to /uff out ! tube dur+ b5d+1 b 9 ?is case !re w\ld be ! difficulty ( remov+ ! fragm5ts1 :i* w\ld be sure to /ick to ! glass4 ,( c\rse1 if ! b5d ne$ n be %ort1 ! tube c\ld be s(t5$ 9 a tube furnace & b5t 9 a k9d ( way4 ,i mu/ admit t ) tubes ( ev5 less ?an "o in* 9 diamet] ,i h g5]ally manag$ be/ by proce$+ little by little4 ,i heat z mu* ( ! glass z ,i c by means ( a gigantic bl[-pipe1 hav+ a nozzle ( ab\t an in* 9 diamet]1 & driv5 by a ma*9e-bl[]4 ,:5 ,i f9d t1 9 spite ( bl[+1 ! tube beg9s to collapse1 ,i susp5d op]ations1 reheat ! tube a little f>!r on1 & s proce$4 ,if by any *ance any read] kn[s a good laboratory me?od ( p]=m+ ?is op]ation1 ,i hope he w communicate x to me4 ,aft] all1 ! difficulty *iefly arises f laboratory heat+ appliances be+ z a rule too limit$ 9 scope = su* "w4 ,! b5d+ ( v ?9 tubes also is a difficulty4 ,i h only succe$$ "h by mak+ v wide b5ds1 b ( c\rse ! bl[+ me?od is q applicable to ?is case1 & ! effect may be obta9$ by weld+ 9 a r ?ick] bit ( tube1 & draw+ & bl[+ x till x is ( ! necess>y ?9ness4 ,?is is1 h[ev]1 a m]e evasion ( ! difficulty4 #cf4 ,spiral ,tubes4 ,^! are easily made :]e good heat+ app>atus is available4 ,z1 h[ev]1 "o con/antly requires to b5d tubes ( ab\t "o-eigh? in* 9 diamet] into spirals 9 ord] to make spr+ connections = cont9u\s glass app>atus1 ,i w describe a me?od by :i* ?is is easily done4 ,provide a bit ( iron pipe ab\t an in* & a qu>t] 9 outside diamet]4 ,cov] ?is ) a ?ick %ea? ( asbe/os clo?1 & sew ! edges ) iron wire4 ,hamm] ! wire d[n s t a good cyl9drical surface is obta9$4 ,make two wood5 plugs = ! ends ( ! iron pipe4 ,bore "o to fit a nail1 :i* may be held 9 a small retort clip1 & fa/5 a /\t wire crank h&le into ! o!r "o4 ,support ! neck ( ! h&le by means ( a second clip4 ,9 ?is way we easily get a sort ( w9dlass q /rong en\gh = our purpose4 ,fig4 #ce4 ,provide a l>ge bl[-pipe1 su* z ! bl[-pipe ( a ,flet*] crucible furnace1 ,select a l5g? ( tub+ & clean x4 ,la% "o end to ! cyl9d] by means ( a bit ( wire1 & hold ! o!r end out ne>ly horizontally4 ,!n />t ! bl[-pipe to play on ! tube j :]e x runs on to ! asbe/os cyl9d]1 & at fir/ "r up to ! la%+4 ,get an att5dant to assi/ 9 turn+ ! h&le ( ! w9dlass1 always keep+ 8 eye on ! tube1 & nev] turn+ s fa/ z to tilt ! tube upw>ds4 ,by means ( ! bl[-pipe1 :i* may be mov$ r\nd ! tub+1 heat ! latt] cont9u\sly z x is drawn ?r\gh ! flame1 & lay x on ! cyl9d] 9 ev5 spirals4 ,if ! tub+ is ?91 a good deal ( c>e w h to be ex]cis$ 9 ord] to prev5t a collapse4 ,a bett] arrangem5t1 :i*1 h[ev]1 ,i h n yet tri$1 w\ld1 ,i ?9k1 be to replace ! bl[-pipe by two bats-w+ burn]s1 p]man5tly fa/5$ to a /&1 "o ( !m play+ its flame d[nw>ds on to ! top ( ! flame ( ! o!r4 ,! angle betwe5 ! directions ( ! jets might be1 say1 #acj1 or :atev] is f\nd conv5i5t4 ,9 ?is way ! glass w\ld n be s likely to get ov]heat$ 9 spots1 & bett] "w w\ld d\btless result4 ,h[ev]1 ,i h made numb]s ( p]fectly satisfactory spirals z describ$4 ,?ree or f\r turns only make a suffici5tly spr+y connection = ne>ly all purposes4 #cg4 ,on ,auxili>y ,op]ations on ,glass3- ,bor+ ,holes ?r\gh ,glass3- ,?is is mu* m easily done ?an is g5]ally suppos$4 ,! be/ mode ( proc$ure dep5ds on ! circum/ances4 ,! foll[+ ?ree cases w be consid]$3- #a4 ,bor+ holes up to "o-qu>t] in* diamet] ?r\gh ?ick glass 7say ov] "o-eigh? in*71 or r l>g] holes ?r\gh ?9 glass4 #b4 ,bor+ holes ( any size ?r\gh ?ick glass4 #c4 ,bor+ r\nd holes ?r\gh ord9>y w9d[ glass4 #ch4 ,bor+ small ,holes4 ,take a ?ree-corn]$ file ( appropriate dim5sions1 & snip ! po9t (f by means ( a hamm]2 gr9d out mo/ ( ! file m>ks to get %>p corn]s4 ,dip ! file 9 k]os5e1 & h pl5ty ( k]os5e at h& 9 a small pot4 ,place ! brok5 end ( ! file aga9/ ! glass1 & ) consid]able pressure beg9 to rotate x 7! file7 backw>ds & =w>ds ) ! f+]s1 v mu* z "o w\ld op]ate a bradawl aga9/ a h>d piece ( wood4 ,! surface ( ! glass w %ortly be gr\nd away1 & !n ! file bradawl w make mu* quick] progress ?an might be expect$4 ,two or ?ree m9utes %\ld suffice to bore a bit ( %eet w9d[-glass4 ,! foll[+ po9ts require att5tion3 7#a7 ,use any quantity ( oil4 7#b7 ,aft] gett+ ?r\gh ! sk9 r$uce ! pressure on ! file4 7#c7 ,be sure to turn ! file backw>ds & =w>ds ?r\gh a complete revolution at lea/4 7#d7 ,:5 ! hole is ne>ly ?r\gh r$uce ! pressure4 7#e7 ,:5 ! hole is ?r\gh ! glass be exce$+ly c>eful n to =ce ! file ?r\gh too rapidly1 o!rwise x w simply act z a w$ge & cause a complete fracture4 7#f7 ,9 _m cases x is bett] to h>d5 ! file 9 m]cury be=e comm5c+ op]ations2 bo? files & glass diff] s mu* 9 h>dness t ?is po9t c only be decid$ by a trial4 ,if x is f\nd necess>y to h>d5 ! file1 use ei!r a l>ge bl[-pipe & a coke or *>coal b$1 or else a small =ge4 ,a small bl[pipe1 su* z is g5]ally f\nd 9 laboratories1 does m h>m ?an good1 ei!r by burn+ ! end ( ! file or rais+ x to an insuffici5t temp]ature4 7#g7 ,to %>p5 ! file1 :i* is (t5 necess>y aft] pass+ ?r\gh ! sk9 ( ! glass1 put x 9 a vice s t ! po9t j protrudes cle> ( ! jaws4 ,!n1 us+ a bit ( wa/e iron z an int]m$i>y anvil or pun*1 knock (f ! lea/ bit f ! po9t1 s z to expose a fre% natural surface4 ,! same result may be br\ght ab\t by ! use ( a pair ( pli]s4 ,if sev]al holes h to be bor$1 x is conv5i5t to m\nt ! file 9 ! la! & use a bit ( flat h>d wood to press up ! glass by means ( ! back re/4 ,a drill+ ma*9e1 if n too heavy1 does v well1 & has ! advantage ( all[+ ! glass to rema9 horizontal s t pl5ty ( oil c be kept 9 ! hole4 ,use a v sl[ spe$ 9 ei!r case--mu* sl[] ?an w\ld be us$ = drill+ wr\ght iron4 ,x is ess5tial t ! lubricant %\ld fl[ on to ! end ( ! file v freely1 ei!r f a pipette or f ! regul> oil-fe$4 ,if a little *ipp+ :]e ! file pi]ces ! back surface is inadmissible1 x is bett]1 on ! :ole1 to f9i% ! bore by h&1 us+ a v tap] file4 ,x is n necess>y to use a special file = ! la!1 = a well-h&l$ file c be *uck$ v conv5i5tly 9 a ?ree-jaw *uck by means ( ! h&le4 ,mr4 ,%5/one recomm5ds a lubricant compos$ ( camphor dissolv$ 9 turp5t9e = g5]al purposes4 ,) ! object ( obta9+ "s decisive in=mation z to ! use ( ?is lubricant1 & to settle o!r po9ts1 ,i made ! foll[+ exp]im5ts4 ,us+ an old ?ree-corn]$ ,fr5* file1 ,i *ipp$ (f ! po9t & adju/$ ! h&le c>efully4 ,i also gr\nd out ! file m>ks ne> ! po9t1 )\t h>d5+ ! file 9 m]cury4 ,us+ k]os5e & turp5t9e & camphor1 ,i began to bore holes 9 a h>d bit ( #c_/cb in* w9d[ glass4 ,ea* hole 0 bor$ to ab\t "o-eigh? in* 9 diamet] 9 f\r m9utes ) ei!r lubricant4 ,aft] h>d5+ ! file 9 m]cury & us+ k]os5e1 ,i also requir$ f\r m9utes p] hole4 ,aft] m\nt+ ! file 9 a la! :i* _h be5 spe$$ to turn up brass rods ( ab\t "o-half-in* diamet]1 & !re=e ran too fa/1 ,i requir$ "o & a half m9utes p] hole1 & bor$ !m "r ?r\gh1 us+ k]os5e4 ,on ! :ole1 ,i ?9k k]os5e does z well z any?+1 & = fil+ is1 ,i ?9k1 bett] ?an ! camphor solution4 ,h[ev]1 ,i ought to say t ! camphor-turp5t9e comp\nd has probably a good deal to recomm5d x1 = x has surviv$ f long ago4 ,my assi/ant tells me he has se5 8 gr&fa!r use x :5 fil+ glass4 ,i beg to ackn[l$ge my indebt$ness to ,mr4 ,pye1 ( ! ,cambridge ,sci5tific ,in/rum5t ,company1 = %[+ me 9 #ahhf 7by ! c\rtesy ( ! ,company7 ! file me?od ( glass-bor+2 x is also describ$ by ,f>aday 9 ,*emical ,manipulation1 #abbh4 ,x is n necess>y1 h[ev]1 to use a file at all1 = ! twi/ drills made by ! ,morse ,drill ,company are q h>d en\gh 9 _! natural /ate to bore glass4 ,! circumf]5tial spe$ ( ! drill %\ld n mu* exce$ #aj feet p] m9ute4 ,9 ?is way ! au?or has bor$ holes ?r\gh glass an in* ?ick )\t any tr\ble except t ( keep+ ! lubricant suffici5tly suppli$4 ,= bor+ v small holes wat*mak]'s drills may be us$ p]fectly well1 especially ^? temp]$ = bor+ h>d5$ /eel4 ,! only difficulty is 9 obta9+ a suffici5t supply ( ! lubricant1 & to secure ?is ! drill mu/ be frequ5tly )drawn4 ,my reason = describ+ ! file me?od at su* l5g? is to be f\nd 9 ! fact t a ,morse drill requires to be %>p5$ aft] drill+ glass be=e x c be us$ 9 ! ord9>y way1 & ?is is (t5 a difficulty4 ,i ought to say t ,i h nev] succe$$ 9 bor+ ! b>rel ( a glass tap by ei!r ( ^! me?ods4 ,footnote3 ,i h be5 lately in=m$ t x is usual to employ a spl9t] ( diamond set 9 a /eel wire hold] bo? = tap bor+ & = drill+ e>!nw>e = rivet+4 ,! diamond mu/1 ( c\rse1 be set s z to give suffici5t cle>ance = ! wire hold]4 ,= me?ods ( us+ & sett+ diamond tools see #ee4 ,x w suffice to say "h t a /eel wire is s(t5$ & fil$ at "o end s z to =m a =k2 into ?is ! diamond is set by squeez+ ) pli]s4 ,! diamond is arrang$ s z to pres5t a po9t 9 ! axis ( ! wire1 & mu/ n project on "o side ( ! wire m ?an on ! o!r4 ,x is n always easy to get a fragm5t satisfy+ ^! conditions1 & at ! same "t suitable = m\nt+4 ,a drop ( sold] occasionally assi/s ! process ( sett+ ! diamond4 ,9 drill+1 ! diamond mu/ be held aga9/ ! "w by a con/ant =ce1 appli$ ei!r by means ( weight or a spr+4 ,i made _m trials by ?is me?od1 us+ a wat*mak]'s la! & press+ up ! "w by a weight & /r+1 :i* pass$ ov] a pulley4 ,i us$ ab\t #dj ounces1 & drill$ a hole #c_/cb 9 diamet] 9 fl9t glass at a spe$ ( #ijj revolutions p] m9ute to a dep? ( "o-eigh? ( an in* 9 eight m9utes4 ,i us$ soap & wat] z a lubricant1 & ! "w 0 satisfactory4 ,s9ce ?is 0 set up1 ,i h be5 in=m$ by ,mr4 ,hicks ( ,hatton ,g>d5 t x is necess>y to anneal glass rod by heat+ x up to ! s(t5+ po9t & all[+ x to cool v sl[ly "u r$-hot s& or asbe/os be=e bor+4 ,if ?is be done1 no tr\ble w be exp]i5c$4 ,! anneal+ mu/ be p]fect4 #ci4 ,= bor+ l>ge holes ?r\gh ?ick glass %eets1 or1 inde$1 ?r\gh any?+ :]e x is necess>y to make sure t no accid5t c happ51 or :]e great precision ( position & =m ( hole is requir$1 ,i f9d a bor+ tube m\nt$ z %[n 9 ! picture 7,fig4 #cf7 is ( great s]vice4 ,brass or iron tube bor]s d p]fectly well1 & ! end ( ! sp9dle may be provid$ once = all ) a small tube *uck1 or ! tubes may be sep>ately m\nt$ z %[n4 ,a fairly high spe$ is desirable1 & may be obta9$ ei!r by foot1 or1 if p[] is available1 is readily got by connect+ to ! spe$ cone ( a la!1 :i* is presumably p]man5tly belt$ to ! motor4 ,fig4 #cf4 ,aft] try+ tubes arm$ ) diamond du/1 z w be pres5tly expla9$1 ,i f9d t em]y & ?9 oil or turp5t9e1 if lib]ally suppli$ bel[ ! glass1 w d v ne>ly z well4 ,! tube %\ld be all[$ to rise f ! "w e few seconds1 s z to all[ ( fre% em]y & oil be+ c>ri$ into ! circul> grooves4 ,?is is done by lift+ ! h+$ upp] be>+1 ! drill be+ lift$ by a spiral spr+ betwe5 ! pulley & ! l[] be>+ %[n at ,b4 ,! glass may be conv5i5tly support$ on a few %eets ( pap] if flat1 or held firm 9 position by wood5 clamps if ( any o!r %ape4 ,9 any case x %\ld be firmly held d[n & %\ld be well support$4 ,any desir$ pressure ^u ! drill is obta9$ by weight+ ! h+$ bo>d ,a4 #dj4 ,! foll[+ me?od 0 %[n to me by ,mr4 ,wim%ur/1 b ,i h n _h occasion to employ x myself4 ,x is suitable = bor+ l>ge holes ?r\gh su* glass z ! plates ( ,mr4 ,wim%ur/'s ,influ5ce ma*9es are usually made (4 ,a diamond is m\nt$ z ! p5cil ( a compass1 & ) ?is a circle is drawn on ! glass 9 ! desir$ position4 ,! o!r leg ( ! compass ( c\rse re/s on a suitable wa%]4 ,to ! be/ ( my recollection ! fur!r proc$ure 0 z foll[s4 ,a piece ( /eel rod ab\t "o-eigh? in* 9 diamet] 0 gr\nd (f flat & m\nt$ 9 a vice v]tically1 s z to cause its plane end to =m a small horizontal anvil4 ,! c5tre 7approximately7 ( ! diamond-cut circle ( ! glass 0 laid on ?is anvil s z to re/ ev5ly ^u x1 & ! upp] surface 7i4e4 t conta9+ ! cut7 0 !n /ruck sm>tly ) a hamm]1 completely pulv]is+ ! glass above ! anvil4 ,! hole 0 gradually ext5d$ 9 a simil> mann] "r up to ! diamond cut1 f :i*1 ( c\rse1 ! glass broke away4 ,a simil> me?od has long be5 kn[n to glazi]s1 diff]+ f ! prec$+ 9 t a s]ies ( diamond cuts are run across ! circle p>allel to two mutually p]p5dicul> diamet]s4 ,a sm>t tap on ! back ( ! scor$ disc w g5]ally cause ! fragm5ts to tumble out4 ,i h nev] tri$ ?is myself1 b ,i h se5 x done4 ,l>ge discs may easily be cut f %eet glass by draw+ a circul> diamond cut1 & gradually break+ away ! out] p>ts by ! aid ( additional cuts & a pair ( pli]s or %anks 7see ,fig4 #dd74 #da4 ,op]ations dep5d+ on ,gr9d+3 ,gr\nd-9 ,jo9ts4 ,! process w be p]fectly und]/ood by ref]5ce to a simple case4 ,suppose x is desir$ to gr9d ! end ( a tube into ! neck ( a bottle4 ,if a /opp]$ bottle is available1 ! /opp] mu/ be tak5 out & measur$ z to its diamet] at ! top & bottom4 ,select a bit ( tube z ne>ly z possible ( ! same diamet] z ! /opp] at its ?icke/ "p4 ,draw d[n ! glass 9 ! bl[-pipe flame r by all[+ x to s9k ?an by pull+ x out4 ,aft] a few trials no difficulty w be exp]i5c$ 9 mak+ its tap] ne>ly equal to t ( ! /opp]1 ?\gh !re w 9 all probability be sev]al ridges & inequalities4 ,:5 ?is /age is rea*$ anneal ! "w c>efully & see t ! glass is n too ?94 ,aft]w>ds use em]y & wat]1 & gr9d ! /opp] into ! bottle4 ,!re are six special directions to be note 7#a 7,turn ! /opp] ?r\gh at lea/ "o revolution 9 ea* direction4 7#b7 ,lift x out (t5 s z to give ! fre% em]y a *ance ( gett+ into ! jo9t4 7#c7 ,rotate ! bottle z well z ! /opp] 9 case !re is any irregul>ity 9 ! =ce br\ght to be>1 :i* might cause "o side ( ! neck to be m gr\nd ?an ano!r1 or w\ld cause ! tube to set r to "o side or ! o!r4 7#d7 ,use em]y pass+ a #ej sieve1 i4e4 a sieve ) fifty ?reads to ! in* run 7see #add7 to beg9 )1 & :5 ! /opp] ne>ly fits1 wa% ?is ?or\ghly away1 & f9i% ) fl\r em]y1 previ\sly wa%$ to get rid ( p>ticles ( excessive size2 ! process ( wa%+ w be fully discuss$ 9 ! *apt] on glass-gr9d+1 :i* see4 7#e7 ,any degree ( f95ess ( surface may be obta9$ by us+ grad$ em]y1 z w be expla9$1 b1 9 g5]al1 x is unnecess>y to attempt a f9] surface ?an c be got ) wa%$ fl\r em]y4 ,a sup]ficial & imp]fect poli% may be giv5 by gr9d+ = a %ort "t ) p[d]$ pumice /one4 7#f7 ,if ! prop] tap] is n atta9$ by bl[+1 or if ridges are left on ! tap]$ "p1 ! process may be bo? ha/5$ & improv$ by giv+ ! tap] a prelim9>y fil+ ) a ?ree-corn]$ file & k]os5e1 j z "o w\ld proce$ ) iron or brass4 ,a little fil+ w (t5 save a good deal ( gr9d+ & make a bett] job4 ,if a bottle )\t a tap]$ neck is to be employ$1 x is z well to d ! prelim9>y gr9d+ by means ( a cone turn$ up f a bit ( ca/ iron4 ,?is is put 9 ! la! & pu%$ into ! m\? ( ! bottle1 ! latt] be+ support$ by ! h&s4 ,use ab\t ! same surface spe$ z w\ld be employ$ = turn+ ca/ iron4 ,9 ?is case ! em]y is bett] us$ ) k]os5e4 ,if a cyl9drical bit ( ca/ iron ab\t an in* 9 diamet] is turn$ d[n conically ne>ly to a po9t1 x w save a good deal ( tr\ble 9 mak+ sep>ate cones4 ,if x gets gr\nd into r+s1 & x becomes necess>y to turn x up1 use a diamond tool until ! sk9 is ?or\ghly remov$2 ! emb$d$ em]y m]ely gr9ds ! edge (f any ord9>y /eel tool4 ,= diamond tools see #ee4 #db4 ,use ( ! ,la! 9 ,glass-work+4 ,if x is necess>y to remove a good deal ( glass1 "t may be sav$ by actually turn+ ! glass 9 a la!4 ,accord+ to ! direction giv5 above = gr9d+ a tube into ! neck ( a bottle1 v little glass ne$ be remov$ if ! draw+ d[n is well done1 s t = ?is purpose turn+ is (t5 unnecess>y4 ,if ! tap] ( ! /opp] be small & x is p]missible to use a ?ick tube1 or if a solid /opp] only has to be provid$1 or an old /opp] quickly alt]$ to a new =m1 turn+ is v useful4 ,! glass may be *uck$ 9 any suitable mann]1 & run at a spe$ n exce$+ #aj feet p] m9ute4 ,prep>e a ?ree-corn]$ file by m]cury-h>d5+ & by gr9d+ ! end flat s z to =m a cutt+ angle ( ab\t #hj1 & use a mod]ate am\nt ( k]os5e lubrication1 i4e4 en\gh to keep ! glass damp1 b ev5 ?is is n ess5tial4 ,use ! file z an ord9>y brass turn+ tool1 & press mu* m lightly ?an = metal turn+4 ,! glass w be f\nd to scrape (f q pleasantly4 ,by *uck+ glass tubes on wood5 m&rells ! ends may be nicely turn$ 9 ?is mann] ready = accurate clos+ by glass plates4 ,! process ( gr9d+ also is made mu* m rapid--at all ev5ts 9 ! e>li] /ages--by *uck+ ei!r ! /opp] or ! bottle & hold+ ! o!r memb] 9 ! f+]s1 or 9 a wood5 vice held 9 ! h&s4 ,! f9i%+ t\*es are be/ giv5 by h&4 ,i ought to say t ,i ?9k a good deal ( glass-gr9d+1 z practis$ 9 laboratories1 might be advantage\sly replac$ by glass turn+ or fil+ & c]ta9ly w be by any "o :o w give ^! me?ods a trial4 ,if "o tube is to be gr\nd into ano!r1 z 9 gr9d+ a retort into a receiv]1 ! latt] mu/ be drawn d[n f a l>g] piece1 few beg9n]s be+ able to wid5 a tube by ! me?od expla9$ ) suffici5t ease & c]ta9ty4 ,! o!r op]ations are simil> to ! op]ations above describ$4 #dc4 ,funnels (t5 require to be gr\nd to an angle ( #fj4 ,= ?is purpose x is well to keep a ca/-iron cone1 tap]+ f no?+ up to f\r in*es 9 diamet]4 ,?is may be m\nt$ on a la!1 & w be f\nd ( great use = gr9d+ out ! inside ( funnels4 ,c>e mu/ be tak5 to "w ! funnel backw>ds & =w>ds1 or x w t5d to gr9d s z to =m r+s1 :i* int]f]e ) filt]+4 ,a r\gh poli% may be giv5 on ! l9es expla9$ 9 ! next section4 #dd4 ,a r\gh poli% may be easily giv5 to a surface :i* has be5 f9i%$ by wa%$ fl\r em]y1 9 ! foll[+ mann]4 ,turn up a disc ( s(t wood on ! la!1 & run x at ! highe/ wood-turn+ spe$4 ,rub into ! p]iph]y a pa/e ( sift$ p[d]$ pumice /one & wat]4 ,any fairly smoo? gr\nd glass surface may be m or less poli%$ by hold+ x = a mom5t aga9/ ! revolv+ disc4 ,exact means ( poli%+ w be describ$ lat] on4 ,mean:ile ?is simple me?od w be f\nd bo? quick & conv5i5t1 & is (t5 q suffici5t :]e transp>5cy1 r ?an figure1 is requir$4 ,i d>esay a f9e poli% may be got on ! same l9es1 us+ putty p[d] or wa%$ r\ge 7n jewell]s' r\ge1 :i* is too s(t1 b glass-poli%]s' r\ge7 to foll[ ! pumice p[d]1 b ,i h n requir$ to try ?is4 #de4 ,x is sometimes requir$ to give to gr\nd glass surfaces a tempor>y transp>5cy4 ,?is is to be done by us+ a film ( oil ( ! same refractive index z ! glass4 ,cornu has employ$ a v>ni% consi/+ ( a mixture ( turp5t9e & oil ( cloves1 b ! yell[-br[n col\r ( ! latt] is (t5 a disadvantage4 ,x w be f\nd t a mixture ( nut oil & oil ( bitt] almonds1 or ( bromo-nap?al5e & acetone1 c be made ( only a fa9t yell[ col\r2 & by exact adju/m5t ( ! proportions w h ! same refractive index = any ray z cr[n glass 7ord9>y w9d[ glass74 ,procure a sample ( ! glass & sma% x up to small fragm5ts 9 an iron mort>4 ,sift out ! f9e du/ & ! l>g] pieces2 bits ab\t z l>ge z small beads--say "o-sixte5? in* e way--d v well4 ,boil ! sift$ glass ) /rong comm]cial hydro*loric acid to remove iron1 wa% ) di/ill$ wat] & a few drops ( alcohol1 dry on blott+ pap] 9 ! sun or o!rwise4 ,put ! dry glass into a bottle or beak]1 & beg9 by add+ almond oil 7or bromo-nap?al5e71 !n add nut oil 7or acetone7 till ! glass practically disappe>s :5 exam9$ by sodium light1 or light ( any o!r wave-l5g?1 z may be requir$4 ,! adju/m5t ( ! mixture is a matt] ( great delicacy1 "o drop too mu* ( ei!r con/itu5t1 91 say1 #ej cubic c5timetres1 makes all ! diff]5ce4 ,! f9al adju/m5t is be/ accompli%$ by hav+ two mixtures ( ! oils1 "o j too ri* 9 almond1 ! o!r 9 nut oil2 by add+ "o or o!r ( ^!1 ! requir$ mixture is soon obta9$4 ,x is to be not$ 7#a7 ,t adju/m5t is only p]fect = light ( "o wave-l5g?4 7#b7 ,t adju/m5t is only p]fect at "o temp]ature4 ,on exam9+ a bottle ( r l>g] fragm5ts ( glass imm]s$ 9 an adju/$ mixture by ord9>y daylight1 a peculi>ly beautiful play ( col\rs is se54 ,( c\rse1 if x is only desir$ to make gr\nd glass fairly transp>5t1 ^! precautions are unnecess>y1 b x seem$ bett] to dispose ( ! matt] once = all 9 ?is connection4 ,m4 ,cornu's object 0 to make a v>ni% :i* w\ld prev5t reflection f ! back ( a photographic plate on to ! film4 ,i h _h occasion to require to d ! same :5 us+ a scale made by cutt+ l9es ?r\gh a film ( black v>ni% on a slip ( glass4 ,?is succe$$ p]fectly by mak+ ! v>ni% out ( ,canada balsam /a9$ ) a black anil9e dye4 ,mr4 ,russell1 ,gov]nm5t ,a/ronom] ( ,new ,s\? ,wales1 f9ds t ! halation ( /> photographs c be prev5t$ by p\r+ ov] ! back ( ! plate a film ( collodion suitably /a9$4 #df4 ,mak+ ,gr\nd ,glass4 ,?is is easily done by rubb+ ! surface ( poli%$ glass ) a bit ( ca/ iron & wa%$ fl\r ( em]y4 ,( c\rse1 if ! f95ess ( gra9 ( ! surface is ( importance1 appropriate sizes ( em]y mu/ be employ$4 ,! iron may be replac$ by a bit ( glass cut ) transv]se grooves to all[ ! em]y to di/ribute itself1 or ev5 by a bit ( glass )\t su* grooves1 provid$ x does n measure m ?an "o or two in*es ea* way4 ,if great spe$ is an object r ?an ! f95ess ( ! surface1 use a bit ( lead & co>se em]y1 say any t w pass a sieve ) fifty ?reads to ! in*4 ,x may p]haps be m5tion$ "h t x is a pity to ?r[ away em]y :i* has be5 us$ betwe5 glass & glass4 ,9 ! *apt] deal+ ) f9e optical "w ! use ( em]y ( v>i\s grades ( f95ess w be treat$1 & ! f9] grades c only be obta9$ 7to my k7 f em]y :i* has be5 cru%$ 9 ! process ( glass or metal gr9d+1 especially ! =m]4 ,a l>ge jam-pot cov]$ ) a c>dbo>d lid does well z a receptacle ( wa%+s4 #dg4 ,glass-cutt+4 ,?is is an art ab\t :i* m c be le>n$ 9 five m9utes by wat*+ x well practis$ ?an by pages ( writt5 description4 ,my advice to any "o ab\t to comm5ce ! practice ( ! art w\ld be to make fri5ds ) a glazi] & see x done4 ,:at foll[s is !re=e on ! supposition t ?is advice has be5 foll[$4 ,aft] "s exp]i5ce ( cutt]s made ( especially h>d5$ /eel1 ,i believe bett] "w c g5]ally be got out ( a diamond1 provid$ ! co/ is n an objection4 ,x is economy to pay a good price = a good diamond4 ,z is well kn[n1 ! natural angle ( ! cry/al makes ! be/ po9t1 & a p]son buy+ a diamond %\ld exam9e ! /one by ! help ( a l5s1 s z to see t ?is condition is fulfill$4 ,! natural angle is g5]ally1 if n always1 b\nd$ by curv$ edges1 :i* h a totally diff]5t appe>ance f ! %>p edges ( a spl9t]4 ,:5 a pur*ase is to be made1 x is z well = ! /ud5t to take a bit ( glass & a foot-rule ) him1 & to te/ ! diamond be=e x is tak5 away4 ,:5 a good diamond has be5 procur$1 beg9 by tak+ cuts on bits ( clean w9d[ glass until ! prop] angle at :i* to hold ! tool is asc]ta9$4 ,nev] try to cut ov] a scrat*1 if y value y\r diamond1 & nev] press h>d on ! glass2 a good cut is accompani$ by an unmi/akable r++ s\nd q diff]5t f ! s\nd made :5 ! diamond is only scrat*+4 ,p]haps ! mo/ important advice t c be giv5 is1 ,nev] l5d ! diamond to anybody--"u any circum/ances4 ,! free use ( a diamond is an art :i* ! physici/ w d well to acquire1 = q a v>iety ( app>atus may be made out ( glass /rips1 & ! accuracy ) :i* ! glass breaks along a good cut r$uces su* an op]ation z glass-box-mak+ to a "q ( accurate draw+4 #dh4 ,cem5t+4 ,"o ( ! matt]s :i* is g5]ally confus$ by too great a pr(usion ( treatm5t is ! art ( cem5t+ glass to o!r sub/ances4 ,! foll[+ me?ods w be f\nd to "w1 subject to two conditions3 7#a7 ,! glass mu/ be clean2 7#b7 x mu/ be hot en\gh to melt ! cem5t4 ,= ord9>y m5d+ purposes :5 ! glass does n require to be plac$ 9 wat] 7especially if hot7 no?+ is bett] ?an t k9d ( glue :i* is g5]ally call$ diamond cem5t4 ,?is may be easily made by dissolv+ ! be/ procurable is+lass 9 a mixture ( #bj p] c5t wat] & #hj p] c5t glacial acetic acid--! exact proportions are n ( consequ5ce4 ,fir/1 ! is+lass is to be tightly pack$ into a bottle ) a wide neck1 !n add ! wat]1 & let ! is+lass soak x up4 ,aft]w>ds p\r 9 ! acetic acid1 & keep ! mixture ne> #ajj;,c4 = an h\r or two on ! wat] ba?--or r 9 x4 ,! total volume ( acetic acid & wat] %\ld n be m ?an ab\t half ( ! volume ( is+lass :5 ! latt] is press$ into ! bottle z tightly z possible4 ,! prop] consi/5cy ( ! cem5t may be asc]ta9$ by lift+ a drop out ( ! bottle & all[+ x to cool on a %eet ( glass4 ,9 t5 m9utes x ought n to be m ?an slightly /icky1 & ! mass 9 ! bottle1 aft] /&+ a few h\rs cold1 %\ld n be /icky at all1 & %\ld yield1 jelly-l1 to ! pressure ( ! f+] to only a slight degree4 ,if ! glue is too weak1 m is+lass may be add$ 7)\t any prelim9>y soak+74 ,a p]son mak+ ! mixture = ! fir/ "t almo/ always gets x too weak4 ,x is difficult to give exact proportions by weight1 z is+lass & gelat9e 7:i* may replace x7 diff] greatly 9 quality4 ,?is cem5t is appli$ l glue1 & w cem5t ne>ly any?+ z well z glass4 ,( c\rse1 z mu* cem5t z possible mu/ be squeez$ out ( any jo9t :]e x is employ$4 ,! addition ( gums1 z recomm5d$ 9 "s books1 is unnecess>y4 ,ord9>y glue w s]ve p]fectly = cem5t+ glass to wood4 ,*ipp$ glass w>e is1 ,i und]/&1 made by pa9t+ clean glass ) glue4 ,z ! glue dries & breaks by contraction1 x *ips (f ! surface ( ! glass4 ,i h nev] se5 ?is done4 ,9 ne>ly all cases :]e alcohol is n to be employ$ v /rong jo9ts may be made by %ellac4 ,orange %ellac is /rong] ?an ! blea*$ v>iety4 ,a s9e qua non is t ! glass be hot en\gh to melt ! %ellac4 ,! be/ way is to heat ! glass surfaces & rub on ! %ellac f a bit ( flake2 ! glass %\ld n be s hot z to discol\r ! %ellac appreciably1 or its valuable prop]ties w be p>tly de/roy$4 ,bo? glass surfaces be+ ?us prep>$1 & ! %ellac be+ q fluid on bo?1 !y may be br\ght toge!r & clamp$ tightly toge!r till cool4 ,%ellac t has be5 ov]heat$1 or dissolv$ 9 alcohol1 or blea*$1 is ( little use z comp>$ ) ! pale orange flaky product4 ,d>k flakes h probably be5 ov]heat$ dur+ ! prelim9>y ref9+4 ,= _m purposes a cem5t is requir$ capable ( resi/+ c>bon bisulphide4 ,?is is easily made by add+ a little treacle 7say #bj p] c5t7 to ord9>y glue4 ,s9ce ! mixture ( glue & treacle does n keep1 i4e4 x _c be satisfactorily melt$ up aga9 aft] once x has set1 no m %\ld be made up ?an w be want$ at ! "t4 ,if ! glue be ?ick1 glass boxes = c>bon disulphide may be easily put toge!r1 ev5 ?\gh ! edges ( ! glass /rips are n q smoo?1 =1 unlike mo/ cem5ts1 ?is mixture rema9s t\gh1 & is fairly /rong 9 itself4 ,i h f\nd by exp]im5t t mo/ fix$ &1 to a less degree1 ess5tial oils h little or no solv5t action on %ellac1 & ,i suspect t ! same rem>k applies to ! treacle-glue mixture1 b ,i h n tri$4 ,turp5es act on %ellac slightly1 b m9]al oils app>5tly n at all4 ,! te/s on :i* ^! /atem5ts are bas$ 7 cont9u$ = ab\t two ye>s1 dur+ :i* "t k]os5e & m9]al oils _h no obs]vable effect on %ellac--fa/5$ galvanomet] mirrors4 #di4 ,fus+ ,electrodes into ,glass4 ,?is art has greatly improv$ s9ce ! introduction ( ! inc&esc5t lamp2 h[ev]1 up to ! pres5t1 plat9um seems to rema9 ! only sub/ance capable ( giv+ a c]ta9ly air-tight result4 ,i h n tri$ ! alum9ium-alum9a me?od4 ,_m ye>s ago x 0 ! fa%ion to surr\nd ! plat9um wire ) a drop ( :ite enamel glass 9 ord] to cause bett] adhesion betwe5 x & ! ord9>y glass4 ,footnote3 ,hittorf & ,geissl] 7,pogg4 ,ann4 #ahfd1 #ce2 ,engli% translation1 ,phys4 ,soc4 ,london1 p4 #ach7 f\nd t x 0 impossible to make air-tight jo9ts betwe5 plat9um & h>d pota% glass1 b t s(t lead glass c\ld be us$ ) success z a cem5t4 ,h[ev]1 9 ! case ( fl9t glass1 if "o may judge f inc&esc5t lamps1 ?is is n ess5tial--a fact :i* entirely co9cides ) my own exp]i5ce4 ,on ! o!r h&1 :5 seal+ electrodes into ,g]man glass ,i h (t5 us$ a drop ( enamel ) p]fect results1 ?\gh ?is is n always done 9 ,g]many4 ,9 all cases1 h[ev]1 9 :i* electrodes h to be seal$ 9--especially :5 !y are liable to heat--,i recomm5d fl9t glass1 & 9 ?is h ! support ( ,mr4 ,ra9 7,! ,inc&esc5t ,lamp & its ,manufacture1 p4 #aca74 ,! exact details = ! prep>ation ( eudiomet] tubes are giv5 by ,f>aday 7,*emical ,manipulation1 #abjj74 ,9 view ( :at has prec$$1 h[ev]1 ,i w cont5t myself ) ! foll[+ notes4 ,make ! hole ?r\gh :i* ! wire is to protrude only slightly l>g] ?an ! wire itself1 & be sure t ! latt] is clean4 ,all[ ! glass to cool suffici5tly n to /ick to ! wire :5 ! latt] is pu%$ 94 ,be sure t1 on heat+1 ! glass does n get r$uc$1 & t x fl[s up to ! wire all r\nd2 pull & pu% ! wire a little ) a pair ( p9c]s1 to ensure ?is4 ,x is n a bad plan to get ! glass exce$+ly fluid r\nd ! wire--ev5 if ! lump has to be bl[n out a little aft]w>ds--z x cools4 ,! seal %\ld f9ally be well anneal$ 9 asbe/os1 b fir/ by gradually mov+ x into ! hot air 9 front ( ! flame4 ,x 0 obs]v$ by ,pr(essor ,j4 ,j4 ,?omson & ! au?or "s ye>s ago 7,proc4 ,roy4 ,soc4 #dj4 #cca4 #ahhf7 t :5 v viol5t dis*>ges are tak5 ?r\gh lightly seal$-9 electrodes 9 lead-glass tubes--say f a l>ge batt]y ( ,leyd5 j>s--gas appe>s to be c>ri$ into ! tube ov] & above t naturally giv5 (f by ! plat9um1 & ?is )\t !re be+ any app>5t want ( p]fection 9 ! seal4 ,?is obs]vation has s9ce be5 confirm$ by o!rs4 ,consequ5tly 9 exp]im5ts on viol5t dis*>ges 9 vacuo :]e c]ta9ty is requir$ z to ! exclusion ( air1 ! seals %\ld be protect$ by a gu>d tube or cap conta9+ m]cury2 ?is mu/1 ( c\rse1 be put 9 hot & clean1 on hot & clean glass1 & 9 special cases %\ld be boil$ 9 situ4 ,a well-kn[n ,g]man physici/ 7,w>burg1 ,i ?9k7 recomm5ds putt+ ! seals "u wat]1 b ,i _c ?9k t ?is is a good plan1 = if air c get 91 :y n wat]8 :i* has its surface t5sion 9 its fav\r4 ,! same reason+ prev5ts my recomm5d+ a lay] ( sulphuric acid above ! m]cury-a me?od us$ = secur+ air-tightness 9 m]cury jo9ts by ,mr4 ,gim+ham1 ,proc4 ,r4 ,s4 #ahgd4 ,fur!r protection may be atta9$ = _m purposes by coat+ ! plat9um wire ) a %ea? ( glass1 say half an in* long1 fus$ to ! plat9um wire to a dep? ( "o-tw5tie? ( an in* all r\nd4 ,9 "s cases ! electrodes mu/ be expect$ to get v hot1 = in/ance1 :5 x is desir$ to plat9ise mirrors by ! device ( ,pr(essor ,wright ( ,yale4 ,9 ?is & simil> cases ,i h met ) great success by us+ b>omet] tubes ( ab\t "o-twelf? ( an in* bore1 & ) walls1 say1 "o-t5? ( an in* ?ick4 ,footnote3 ,b>omet] tube is m]ely v ?ick-wall$ glass tub+1 & makes p>ticul>ly bad b>omet]s1 :i* are sold z wea!r glasses4 ,?is tube is drawn d[n to a long po9t--say an in* long by "o-eigh? ( an in* ext]nal diamet]1 & ! wire is fus$ 9 = a l5g?1 say1 ( ?ree-qu>t]s ( an in*1 b only 9 ! n>r[ drawn--d[n "p ( ! tube4 ,at diff]5t times ,i h tri$ f\r su* seals1 & ?\gh ! electrodes 7 r$ hot = h\rs1 ,i h nev] _h an accid5t--( c\rse !y 7 well anneal$4 ,fig4 #cg4 ,= directions z to ! mak+ ( high vacuum tubes1 see ! section deal+ ) t matt]4 #ej4 ,z economy ( plat9um is (t5 ( importance1 ! foll[+ little art w save money & tr\ble4 ,plat9um is easily caus$ to jo9 mo/ firmly to copp]--) :i*1 ,i presume1 x alloys--by ! foll[+ me?od4 ,hold ! plat9um wire aga9/ ! copp] wire1 end to end1 at ! tip ( ! r$uc+ flame ( a typical bl[pipe--or any:]e--pref]ably 9 ! r$uc+ "p ( ! oxygas flame2 9 a mom5t ! metals w fuse toge!r at ! po9t ( contact1 :5 !y may be )drawn4 ,su* a jo9t is v /rong & :olly satisfactory1 mu* bett] ?an a sold]$ jo9t4 ,if ! "w is n c>ri$ out successfully s t a consid]able drop ( copp]-plat9um alloy accumulates1 cut x (f & />t aga94 ,! ess5ce ( success is spe$1 s t ! copp] does n get burn$4 ,if any consid]able quantity ( alloy is =m$ x dissolves ! copp]1 & weak5s x1 s t we h fir/ ! plat9um wire1 !n a bead ( alloy1 & !n a copp] wire fus$ into ! bead1 b s ?9 j outside ! latt] t ! jo9t has no me*anical /r5g?4 #ea4 ,! ,art ( mak+ ,air-light ,jo9ts4 ,lamp-manufactur]s & o!rs h long s9ce le>n$ t :5 glass is 9 "q n only are fus$ jo9ts made z easily z o!rs1 b t !y af=d ! only reliable =m ( jo9t4 ,an exp]im5t] :o uses fl9t glass1 has a little exp]i5ce1 an oxygas bl[-pipe & a bl[+ app>atus1 w pref] to make 8 jo9ts 9 ?is way1 simply f ! ease ) :i* x may be done4 ,:5 x comes to mak+ a tight jo9t betwe5 glass & o!r sub/ances ! problem is by no means s easy4 ,?us ,mr4 ,griffi?s 7,phil4 ,trans4 #ahic1 p4 #chj7 fail$ to make air-tight jo9ts by cem5t+ glass into /eel tubes1 us+ h>d %ellac1 & ! tubes fitt+ closely4 ,^! jo9ts 7 satisfactory at fir/1 b did n la/2 ! l5g? ( ! jo9t is n /at$4 ,! difficulty 0 f9ally got ov] by sold]+ v n>r[ plat9um tubes into ! /eel1 & fus+ ! =m] into ! glass4 ,mr4 ,griffi?s has s9ce us$ an alloy ) success z a cem5t1 b ,i _c discov] :at x is made f4 ,_m ye>s ago ,pr(essor ,hittorf prep>$ good high vacuum tubes by plugg+ ! ends ( glass tubes ) seal+ wax m]ely1 ?\gh 9 all cases ! spaces to be fill$ ) wax 7 long & n>r[ 7,hittorf1 ,pogg4 ,ann4 #ahfi1 #e1 ,engli% translation1 ,phys4 ,soc4 p4 #aac74 ,aga91 ,regnault habitually us$ brass f]ules1 & cem5t$ glass into !m by means ( 8 ma/ic1 :i* c /ill be procur$ at a l[ rate f 8 in/rum5t-mak]s 7,golan1 ,p>is74 ,l5>d also1 9 8 inve/igations on ,ca?ode ,rays 7,wi$4 ,ann1 vol4 li4 p4 #bbd71 made use ( seal+ wax cov]$ ) m>9e glue4 ,surely 9 face ( ^! facts we mu/ admit t cem5t jo9ts c be made ) fair success4 ,i d n "k ! composition ( ,m4 ,regnault's ma/ic1 b ,f>aday 7,manipulations1 #aabc7 gives ! foll[+ receipt = a cem5t = jo9+ f]ules to retorts1 etc3 ,res9 #e p>ts4 ,beeswax #a "p4 ,r$ o*re or ,v5etian r$1 f9ely p[d]$ & sift$ #a "p4 ,i believe ?is to be sub/antially ! same z ,regnault's ma/ic1 ?\gh ,i h nev] analys$ ! latt]4 ,= *emical "w ! possibility ( evolution ( gas f su* a cem5t mu/ be tak5 into acc\nt1 & ,i %\ld c]ta9ly n tru/ x = ?is reason 9 vacuum tube "w1 :]e ! purity ( ! conf9$ gas c\ld come 9 "q4 ,o!rwise x is an excell5t cem5t1 & does n 9 my exp]i5ce t5d to crack away f glass to ! same ext5t z p>aff9 or pure %ellac4 ,?is crack+ away f glass1 by ! way1 is probably an effect ( diff]5ce 9 rate ( expansion betwe5 ! glass & cem5t :i* probably always exi/s1 &1 if ! cem5t be n suffici5tly visc\s1 mu/1 beyond c]ta9 temp]ature limits1 ei!r produce cracks or cause sep>ation4 ,pr(essor ,wright ( ,yale has us$ a h>d m9]al pit* z a cem5t 9 vacuum "w ) success4 ,my att5tion has be5 direct$ to a fusible metal cem5t conta9+ m]cury1 & made accord+ to ! foll[+ receipt1 giv5 by ,mr4 ,s4 ,g4 ,rawson1 ,j\rnal ( ! ,society ( ,*emical ,indu/ry1 vol4 ix4 7#ahij71 ,p4 #aej3- ,bismu? #dj p] c5t ,lead #be p] c5t ,t9 #aj p] c5t ,cadmium #aj p] c5t ,m]cury #ae p] c5t ,?is is practically "o =m ( ,rose's fusible metal ) #ae p] c5t m]cury add$4 ,x takes ne>ly an h\r to set completely1 & ! app>atus mu/ be clean & w>m be=e x is appli$4 ,z ! result ( sev]al trials by myself & fri5ds1 ,i am afraid ,i mu/ diss5t f ! claim ( ! au?or t su* a cem5t w make a really air-tight jo9t betwe5 glass tubes4 ,inde$1 ! appe>ance ( ! surface z view$ ?r\gh ! glass is n su* z to give any confid5ce1 no matt] :at c>e may h be5 ex]cis$ 9 p]=m+ all ! op]ations & clean+ ! glass2 besides :i* ! cem5t is rigid :5 cold1 & ! expansion difficulty comes 94 ,on ! o!r h&1 if extreme air-tightness is n an object1 ! cem5t is /rong & easily appli$1 & has _m uses4 ,i h an idea t if ! jo9ts 7 cov]$ ) a lay] ( s(t wax1 ! result w\ld be satisfactory 9 s f> z air-tightness is conc]n$4 ,?is anticipation has s9ce be5 v]ifi$4 ,9 _m cases "o c resort to ! device already m5tion$ ( enclos+ a rubb] or tape-wrapp$ jo9t betwe5 two tubes 9 a ba? ( m]cury1 b 9 ?is case ! glass mu/ be clean & hot & ! m]cury also w>m1 dry1 & pure :5 ! jo9t is put toge!r1 o!rwise an appreciable air film is left aga9/ ! glass1 & ?is may creep into ! jo9t4 ,p]haps ! easie/ way ( mak+ su* a jo9t is to use an out] tube ( ?9 clean glass1 & bore a n>r[ hole into x f "o side to admit ! m]cury2 if ! m]cury is to be heat$ 9 vacuo1 x is bett] to seal on a side jo9t4 ,x is always bett]1 if possible1 to boil ! m]cury 9 situ1 :i* involves mak+ ! wrapp+ ( asbe/os1 b1 aft] all1 we come back to ! position ,i began by tak+ up1 viz4 t ! easie/ & mo/ reliable me?od is by fusion ( ! glass--all ! re/ are unsuitable = "w ( real precision4 ,i %\ld be ungrateful1 h[ev]1 7 ,i n to devote a few l9es to ! great conv5i5ce & m]it ( s-call$ c5t]+ cem5t4 ,?is sub/ance has two or ?ree v valuable prop]ties4 ,x is v t\gh & /rong 9 itself1 & x rema9s pla/ic on cool+ = "s "t be=e x really sets4 ,if = any reason a small tube has to be cem5t$ into a l>g] "o1 :i* is a good deal l>g]1 s t an appreciable mass ( cem5t is necess>y1 & p>ticul>ly if ! jo9t requires to h great me*anical /r5g?1 ?is cem5t is invaluable4 ,i h ev5 us$ a plug ( x in/ead ( a cork = mak+ ! jo9t betwe5 a gas deliv]y tube & a calcium *loride t[]4 7,:y are ^! affairs made ) su* abom9able tubulures87 ,! jo9t 9 "q has nev] all[$ ! tube to sag ?\gh x projects horizontally to a di/ance ( #f in*es1 & has _h to )/& ne>ly two ye>s ( ,sydney temp]ature4 ,! cem5t consi/s ( a mixture ( %ellac & #aj p] c5t ( oil ( cassia4 ,! %ellac is fir/ melt$ 9 an iron ladle1 & ! oil ( cassia quickly add$ & /irr$ 91 to an ext5t ( ab\t #aj p] c5t1 b ! exact proportions are n ( importance4 ,great c>e mu/ be tak5 n to ov]heat ! %ellac4 ,,app5dix ,,to ,,*apt] ,i ,,on ,,! ,,prep>ation ,,( ,,vacuum ,,tubes ,,= ,,! ,,production ,,( ,,pr(essor ,,ro5tg5',s ,,radiation ,footnote3 ,writt5 9 ,may #ahif4 ,,:5 ,pr(essor ,ro5tg5's discov]y 0 fir/ ann\nc$ at ! end ( #ahie mu* difficulty 0 exp]i5c$ 9 obta9+ radiation ( ! requisite int5sity = ! repetition ( 8 exp]im5ts4 ,! foll[+ notes on ! production ( vacuum tubes ( ! requir$ quality may !re=e be ( use to ^? :o desire to prep>e _! own app>atus4 ,x appe>s t fl9t glass is mu* m opaque to ,ro5tg5's radiation ?an soda glass1 & consequ5tly ! vacuum tubes require to be prep>$ f ! latt] mat]ial4 ,fig4 #ci4 ,a =m ( vacuum tube :i* has prov$ v successful 9 ! au?or's h&s is sket*$ 9 ,fig4 #ch4 ,x is mo/ easily con/ruct$ z foll[s4 ,a bit ( tub+ ab\t #b c5timetres diamet]1 #ae c5timetres long1 & #a4e millimetre wall ?ickness1 is drawn d[n to a po9t4 ,! l>g] bulb1 ab\t #e c5timetres 9 diamet]1 is bl[n at "o end ( ?is tube4 ,! ?9n] ! bulb ! bett]1 provid$ t x does n collapse "u atmosph]ic pressure4 ,a v good idea ( a prop] ?ickness may be obta9$ f ! /atem5t t ab\t #d c5timetres l5g? ( ! tub+ %\ld be bl[n out to =m ! bulb4 ,?is w\ld give a bulb ( ab\t ! ?ickness ( an ord9>y fractionat+ bulb4 ,be=e go+ any fur!r x is z well to te/ ! bulb by tapp+ on ! table & by exhau/+ x by means ( an ord9>y wat]-velocity pump4 ,! side tube is next prep>$ out ( n>r[] tub+1 & is provid$ ) a small] bulb1 a bl[+-out tube1 & a t]m9al1 to be made z w be describ$4 ,?is side tube is next fus$ on to ! ma9 tube1 special c>e be+ tak5 ab\t ! anneal+1 & ! ca?ode t]m9al is !n seal$ into ! ma9 tube4 ,aft] us+ clean glass x is 9 g5]al only necess>y to r9se ! tube out ) clean alcohol1 aft] :i* x may be dri$ & exhau/$4 ,! success ( ! op]ation w dep5d prim>ily on ! att5tion giv5 to ! prep>ation & seal+-9 ( ! electrode fac+ ! l>ge bulb4 ,prep>ation ( ,t]m9als4 ,"s plat9um wire ( ab\t ,no4 #bf ,b4,w4,g--! exact size is unimportant--mu/ be provid$1 also "s %eet alum9ium ab\t #a millimetre ?ick1 "s :ite enamel cem5t glass1 & a cane ( fl9t-glass tube ( a few millimetres bore4 ,! electrodes are prep>$ by cutt+ discs ( alum9ium ( f #a to #a4e c5timetres diamet]4 ,! discs ( alum9ium are bor$ 9 ! c5tre1 s z to admit ! /ems :i* are made ( alum9ium wire ( ab\t #a millimetre diamet]4 ,! /ems are !n rivet$ into ! discs4 ,! /ems are ab\t ,i c5timetre long1 & are drill$ to a dep? ( ab\t #c millimetres1 ! drill us$ be+ ab\t d\ble ! diamet] ( ! plat9um wire to be us$ = mak+ ! connections4 ,! faces ( ! electrodes--i4e4 ! free surfaces ( ! alum9ium discs--are !n hamm]$ flat & br\ght to a burni%$ surface by be+ plac$ on a bit ( highly poli%$ /eel & /ruck by a set provid$ ) a hole to all[ ( ! /em escap+ damage4 ,! op]ation w be obvi\s aft] a ref]5ce to ,figs4 #ci & #dj2 x is ref]r$ to aga9 on page #if4 ,! plat9um wires may be mo/ conv5i5tly atta*$ by melt+ "o end ( ! piece ( plat9um wire 9 ! oxygas bl[-pipe till x =ms a bead j l>ge en\gh to pass into ! hole drill$ up ! /em ( ! electrode4 ,! junction betwe5 ! /e9 & ! plat9um wire is !n made p]man5t by squeez+ ! alum9ium d[n ^u ! plat9um wire ) ! help ( a pair ( pli]s4 ,x is also possible to fuse ! alum9ium r\nd ! plat9um1 b z ,i h _h sev]al breakages ( su* jo9ts1 ,i pref] ! me*anical connection describ$4 ,fig4 #ci4 ,sets = /rik+ alum9ium electrodes ,fig4 #dj4 i4 ,alum9ium electrode4 ii4 ,alum9ium electrode connect$ to plat9um wire4 iii4 ,alum9ium electrode connect$ to plat9um wire & protect$ by glass4 iv4 ,detail ( fa/5+ plat9um wire4 ,! /em & plat9um wire may n[ be protect$ by cov]+ !m ) a little fl9t glass4 ,= ?is purpose ! fl9t-glass tube is pull$ d[n till x w j slip ov] ! /em & wire1 & is cut (f s z to leave ab\t half a c5timetre ( plat9um wire project+4 ,! fl9t-glass tube is !n fus$ d[n ^u ! plat9um wire1 c>e be+ tak5 to avoid ! pres5ce ( air bubbles4 ,at ! close ( ! op]ation a s+le drop ( :ite enamel glass is fus$ r\nd ! plat9um wire at a high temp]ature1 s z to make a good jo9t ) ! protect+ fl9t-glass tube4 ,! negative electrode be+ ne>ly z l>ge z ! ma9 tube1 x mu/ be introduc$ be=e ! latt] is drawn d[n = seal+4 ,aft] draw+ d[n ! ma9 tube 9 ! usual mann]1 tak+ c>e n to make x less ?an a millimetre 9 wall-?ickness1 x is cut (f s z to leave a hole n q big en\gh = ! enamel drop to pass ?r\gh4 ,by heat+ & op5+1 ! ap]ture is got j l>ge en\gh to all[ ! enamel drop to pass into x1 & :5 ?is is ! case ! jo9t is seal$1 pull$1 & bl[n out until ! electrode occupies ! "r position--viz4 9 ! c5tre ( ! tube & ) its face normal to ! axis ( ! tube4 ,! glass walls ne> ! negative electrode mu/ n be less ?an a millimetre ?ick1 & may be r m ) advantage1 ! glass mu/ be ev51 & ! jo9t betwe5 ! fl9t glass & ! soda glass1 or betwe5 ! wire & ! soda glass1 mu/ be :olly ?r\gh ! enamel4 ,! seal mu/ be well anneal$4 ,x w be f\nd t ! seal+-9 process is mu* easi] :5 ! /em ( ! electrode is %ort & :5 ! glass coat+ is n too heavy4 ,half a millimetre ( glass ?ickness r\nd ! /e9 is q suffici5t4 ,! diagram1 ( ! tube %[s t ! ma9 tube has be5 exp&$ r\nd ! edges ( ! ca?ode4 ,?is is to r$uce ! heat+ consequ5t on ! projection ( ca?ode rays f ! edges ( ! disc aga9/ ! glass tube4 ,! anode is ins]t$ into its bulb 9 a q simil> mann]4 ,if desir$ x may be made consid]ably small]1 & does n ne$ ! c>eful adju/m5t requisite 9 seal+-9 ! ca?ode1 nor does ! glass ne> ! entry wire require to be s ?ick4 ,m int5se effects are (t5 got by mak+ ! ca?ode slightly concave1 b 9 ?is case ! risk ( melt+ ! ?9 glass is consid]ably increas$4 ,no d\bt1 ,bohemian glass might be us$ ?r\gh\t in/ead ( s(t soda glass1 & ?is w\ld n melt s easily2 ! difficulties ( manipulat+ ! glass are1 h[ev]1 m pron\nc$4 ,x w be %[n directly t ! be/ ,ro5tg5 effects are got ) a high vacuum1 & x is = ?is reason t ! glass ne> ! ca?ode seal requires to be /rong4 ,! pot5tial "r up to ! ca?ode is /rongly positive inside ! tube1 & ?is causes ! glass to be expos$ to a /rong electric /ress 9 ! neighb\rhood ( ! seal4 ,al?\gh ! glass-bl[+ involv$ 9 ! mak+ ( a s-call$ focus tube is r m difficult ?an 9 ! case j describ$1 !re is no reason :y su* a difficulty %\ld n be ov]come2 ,i w !re=e expla9 h[ a focus tube may be made4 ,fig4 #da4 ,a bulb ab\t #c in*es 9 diamet] is bl[n f a bit ( tube ( a little m ?an #a in* diamet]4 ,unless ! walls ( ! tube are ab\t "o-eigh? ( an in* 9 ?ickness1 ?is w involve a prelim9>y ?ick5+ up ( ! glass4 ,?is is n difficult if c>e be tak5 to avoid mak+ ! glass too hot4 ,! l>g] gas jet describ$ 9 connection ) ! soda-glass-bl[+ table mu/ be employ$4 ,9 bl[+ a bulb ( ?is size x mu/ n be =gott5 t draughts ex]cise a v injuri\s influ5ce by caus+ ! glass to cool unequally2 ?is leads to bulbs ( irregul> %ape4 ,9 ! me?od ( con/ruction %[n 9 ,fig4 #da1 ! anode is put 9 fir/4 ,?is anode simply consi/s ( a squ>e bit ( plat9um or plat9um-iridium foil1 measur+ ab\t #j4ge in* by #a in*1 & rivet$ on to a b5t alum9ium wire /em4 ,z soon z ! anode is fus$ 91 & :ile ! glass is /ill hot1 ! side tube is put on4 ,! :ole ( ! anode end is !n c>efully anneal$4 ,:5 ! anneal+ is f9i%$ ! side tube is b5t z %[n to s]ve z a h&le :5 ! "t comes to m\nt ! ca?ode4 ,be=e plac+ ! ca?ode 9 position1 & :ile ! ma9 tube is /ill wide op51 ! anode is adju/$ by means ( a tool ?ru/ 9 ?r\gh ?is op5 end4 ,?is is necess>y 9 view ( ! fact t ! plat9um foil is occasionally b5t dur+ ! op]ation ( =c+ ! anode into ! bulb4 ,! ca?ode is a portion ( a sph]ical surface ( poli%$ alum9ium1 a mode ( prep>+ :i* w be giv5 directly4 ,! ca?ode hav+ be5 plac$ inside ! bulb1 ! wide glass tube is c>efully drawn d[n & cut (f at su* a po9t t :5 ! ca?ode is 9 position its c5tre ( curvature w lie slightly 9 front ( ! anode plate4 ,= in/ance1 if ! radius ( curvature ( ! ca?ode be #a4e in*es1 ! c5tre ( curvature may lie some?+ l an eigh? ( an in* or less 9 front ( ! anode4 ,! ca?ode z %[n 9 ,fig4 #da is r small] ?an is advantage\s4 ,to make x mu* l>g] ?an is %[n1 h[ev]1 ! op5+ into ! bulb w\ld require to be consid]ably wid5$1 & ?\gh ?is is n really a difficult op]ation1 /ill x requires m practice ?an my read]s are likely to h _h4 ,! difficulty is n s mu* 9 wid5+ out ! entry z 9 clos+ x d[n aga9 neatly4 ,n[ z to mak+ ! anode4 ,a disc ( alum9ium is cut f a %eet :i* mu/ n be too ?ick--"o tw5ty-fif? ( an in* is q ?ick en\gh4 ,?is disc is bor$ at ! c5tre to all[ ( ! /em be+ rivet$ 9 position4 ,! disc is !n anneal$ 9 ! ,buns5 flame & ! /em rivet$ on4 ,! curvature is be/ got by /rik+ betwe5 /eel dies 7see ,figs4 #ci & #dj74 ,two bits ( tool /eel are s(t5$ & turn$ on ! la!1 "o convex & ! o!r concave4 ,! concave die has a small hole drill$ up ! c5tre to admit ! /em4 ,! desir$ radius ( curvature is easily atta9$ by cutt+ out templates f %eet z9c & us+ !m to gauge ! turn+4 ,! two dies are slightly gr\nd toge!r on ! la! ) em]y & oil & are !n poli%$1 or r ! convex die is poli%$--! o!r "o does n matt]4 ,! poli%+ is mo/ easily done by us+ grad$ em]y & oil & poli%+ ) a rag4 ,! me?od ( grad+ em]y w be describ$ 9 ! *apt] on glass-gr9d+4 ,! alum9ium disc is n[ /ruck betwe5 ! dies by means ( a hamm]4 ,if ! radius ( curvature is any?+ m ?an "o in* & ! disc n m ?an "o in* 9 diamet] ! ca?ode c be /ruck at once f ! flat z describ$4 ,= v deep curves no d\bt x w be bett] to make an int]m$iate pair ( dies & to re-anneal ! alum9ium aft] ! fir/ /rik+4 ,:5 ! tube is successfully prep>$ s f> z ! glassbl[+ goes x may be r9s$ ) /rong pure alcohol bo? inside & out1 & dri$4 ,! /raight "p ( ! side tube is !n con/rict$ ready = fus+ (f & ! :ole affair is plac$ on ! vacuum pump4 ,9 spite ( ! great improvem5ts made dur+ rec5t ye>s 9 ! con/ruction ( s-call$ ,geissl] vacuum pumps--i4e4 pumps 9 :i* a ,torricellian vacuum is cont9ually reproduc$--,i am ( op9ion t ,spr5gel pumps are1 on ! :ole1 m conv5i5t = exhau/+ ,crooke's tubes4 ,a full discussion ( ! subject ( vacuum pumps w be f\nd 9 a "w by ,mr4 ,g4 ,s4 ,ram 7,! ,inc&esc5t ,lamp & its ,manufacture71 publi%$ by ! ,electrician ,publi%+ ,company1 & x is n my int5tion to deal ) ! matt] "h2 ! simple/ k9d ( ,spr5gel pump w be f\nd q adequate = our purpose1 provid$ t x is well made4 ,fig4 #db is int5d$ to repres5t a modification ( a pump bas$ on ! model manufactur$ by ,hicks ( ,hatton ,g>d51 & arrang$ to suit ! amateur glass-bl[]4 ,! only po9t ( importance is ! con/ruction ( ! head ( ! fall tube1 ( :i* a sep>ate & enl>g$ diagram is giv54 ,! fall tubes may h an int]nal diamet] up to #b mm4 7two millimetres7 & an effective l5g? ( #abj cm4 ,free use is made ( rubb] tube connections 9 ! "p ( ! pump expos$ to ! passage ( m]cury4 ,! rubb] employ$ %\ld be black & ( ! highe/ quality1 hav+ ! walls /r5g!n$ by a lay] ( canvas4 ,if su* tube _c be easily obta9$1 a v good sub/itute may be made by plac+ a bit ( ord9>y black tube inside ano!r & r l>g] bit & b9d+ ! out] tube ) tape or ribbon4 ,9 any case ! tub+ :i* comes 9 contact ) ! m]cury %\ld be boil$ 9 /rong cau/ic pota% or soda solution = at lea/ t5 m9utes to get rid ( free sulphur1 :i* f\ls ! m]cury directly x comes 9 contact ) x4 ,! tub+ is well wa%$1 r9s$ ) alcohol1 & c>efully dri$4 ,fig4 #db4 ,! diagram repres5ts :at is practically a sy/em ( ?ree ,spr5gel pumps1 ?\gh !y are all f$ f ! same m]cury res]voir & run d[n into ! same m]cury receiv]4 ,x is mu* easi] to make ?ree pumps1 ea* ) sep>ate p9* cocks to regulate ! m]cury supply1 ?an x is to make ?ree jets1 ea* deliv]+ exactly ! prop] /ream ( m]cury to ?ree fall tubes4 ,spr5gel pumps only "w at _! highe/ effici5cy :5 ! m]cury supply is c>efully regulat$ to suit ! peculi>ities ( ea* fall tube1 & ?is is q easily done 9 ! model figur$4 ,s9ce on />t+ ! pump ! rubb] connections h to /& a consid]able pressure1 ! ends ( ! tubes mu/ be some:at corrugat$ to enable ! rubb] to be firmly wir$ on to !m4 ,! be/ b9d+ wire is ! pure/ ,sw$i% iron wire1 previ\sly anneal$ 9 a ,buns5 gas flame4 ,! wire mu/ nev] be twi/$ d[n on ! b>e rubb]1 b mu/ always be sep>at$ f x by a tape b9d+4 ,by tak+ ?is precaution ! wire maybe twi/$ v mu* m tightly ?an is o!rwise possible )\t cutt+ ! rubb]4 ,! only difficulty 9 mak+ su* a pump z is describ$ lies 9 ! b5d+ ( ! heads ( ! fall tubes4 ,?is b5d+ mu/ be done ) p]fect regul>ity & neatness1 o!rwise ! drops ( m]cury w n break regul>ly1 or w break j inside ! top ( ! fall tube1 & s ob/ruct its entrance t at high vacua no air c get into ! tube at all4 ,! connections at ! head ( ! fall tubes mu/ also be well put on & ! jo9ts bl[n out s t ! m]cury 9 dropp+ ov] ! head is n int]f]$ ) by ! upp] surface ( ! tube4 ,h[ev]1 a glance at ! enl>g$ diagram w %[ :at is to be aim$ at bett] ?an any am\nt ( description4 ,9 prep>+ ! fall tubes x is g5]ally necess>y to jo9 at lea/ two canes toge!r4 ,! jo9t mu/ be arrang$ to occur ei!r 9 ! tube lead+ ! m]cury to ! head ( ! fall1 or 9 t "p ( ! fall tube :i* rema9s full ( m]cury :5 ! highe/ vacuum is atta9$4 ,on no acc\nt mu/ ! jo9t be made at ! fall itself 7at lea/ n by an amateur71 nor 9 t "p ( ! fall tube :]e ! m]cury falls freely1 p>ticul>ly at its l[] end1 :]e ! drops fall on ! head ( ! column ( m]cury4 ,:5 a high vacuum is atta9$ ! efficacy ( ! pump dep5ds *iefly on ! way 9 :i* ! drops fall on ! head ( ! column4 ,if ! fall is too long ! drops are apt to break up & all[ ! small bubble ( air to escape up ! tube1 also any irregul>ity or dirt 9 ! tube at ?is po9t makes x m easy = ! bubbles ( air to escape to ! surface ( ! m]cury4 ,any pump 9 :i* ! supply ( m]cury to ! fall tube c be regulat$ nicely w pump well until ! l[e/ available pressures are be+ atta9$2 a good pump w !n cont9ue to hold ! air bubbles1 :ile a bad "o w all[ !m to slip back ,footnote3 ,= special me?ods ( avoid+ ?is difficulty see ,mr4 ,ram's book4 444 ,?\gh ?ree fall tubes are recomm5d$1 x mu/ n be suppos$ t ! pump w produce a ,crooke's vacuum ?ree times m rapidly ?an "o fall tube4 ,until ! m]cury comm5ces to hamm] 9 ! pump ! ?ree tubes w pump approximately ?ree times fa/] ?an "o tube1 b z soon z ! major portion ( ! air collect$ beg9s to come f ! lay] cond5s$ on ! glass surface ( ! tube to be exhau/$ & f ! electrodes1 ! rate at :i* exhau/ion w g on no long] dep5ds entirely on ! pump4 ,9 ord] t bubbles ( air may n slip back up ! fall tube x is g5]ally desirable to all[ ! m]cury to fall pretty briskly1 & 9 ?is case ! capacity ( ! pump to take air is g5]ally f> 9 excess ( ! air supply4 ,"o advantage ( hav+ m ?an "o fall tube is t x (t5 happ5s t a fall tube gets soil$ dur+ ! process ( exhau/ion & no long] works up to its be/ p]=mance4 ,out ( ?ree fall tubes1 h[ev]1 "o is pretty sure to be work+ well1 & z soon z ! m]cury beg9s to hamm] 9 ! tubes ! supply may be %ut (f f ! two falls :i* are work+ lea/ satisfactorily4 ,?us we are enabl$ to pump rapidly till a high degree ( exhau/ion is atta9$1 hav+ practically ?ree pumps in/ead ( "o1 :]eas :5 ! f9al /ages are rea*$1 & ?ree pumps are only a drawback 9 t !y increase ! m]cury fl[1 ! app>atus is capable ( in/ant modification to meet ! new conditions4 ,! ?i/le funnels at ! head ( ! fall tubes are made simply by bl[+ bulbs & !n bl[+ ! heads ( ! bulbs into wid] ones1 & f9ally bl[+ ! heads ( ! wid] bulbs (f by vigor\s bl[+4 ,! /opp]s are gr\nd 9 on ! la! be=e ! tubes are atta*$ to ! fall tubes4 ,! /opp]s require to be at lea/ half an in* long :]e !y fit ! necks1 & mu/ be really well gr\nd 94 ,! /opp]s mu/ fir/ be turn$ up nicely & ! necks gr\nd out by a copp] or iron cone & em]y4 ,! /opp]s are rotat$ on a la! at q a sl[ spe$1 say #cj or #dj feet p] m9ute1 & ! necks are held aga9/ !m1 z describ$ 9 ! section deal+ ) ?is art4 ,! /opp]s mu/ 9 ?is case be f9i%$ ) two seconds em]y1 & la/ly ) pumice du/ & wat] 7see *apt] on glass-gr9d+74 ,unless ! /opp]s fit exce$+ly well tr\ble w arise f ! m]cury 7:i* is p\r$ into ! ?i/le heads to =m a seal7 be+ =c$ d[nw>ds into ! pump by atmosph]ic pressure4 ,! jo9ts betwe5 ! ?ree fall tubes & ! s+le exhau/ ma9 are easily made :5 ! tubes are f9ally m\nt$1 ! hook$ nozzle ( ! oxygas bl[-pipe be+ expressly made = su* "w4 ,x is1 on ! :ole1 advisable to make ! pump ( fl9t glass1 or at all ev5ts ! air-trap tube & ! fall tubes4 ,a bru% flame f ! l>g] gas tube ( ! s+le bl[pipe table is mo/ suitable = ! "w ( b5d+ ! tubes4 ,! jo9t+ ( ! long1 n>r[ bore fall tubes is be/ accompli%$ by ! oxygas flame1 = 9 ?is way ! m9imum ( irregul>ity is produc$2 ! bl[+ tubes w ( c\rse be requir$ = ! job1 & ! n>r[ tubes mu/ be well clean$ to beg9 )4 ,! air trap is an important ?\gh simple "p ( ! pump4 ,its %\ld] or fall %\ld /& r high] ?an ! %\ld]s ( ! fall tubes1 s t ! m]cury may run 9 a ?9 /ream ?r\gh a good ,torricellian vacuum be=e x passes d[n to ! fall tubes4 ,?is is easily atta9$ by regulat+ ! ma9 m]cury supply at ! p9* cock situat$ betwe5 ! tube f ! upp] res]voir & ! air-trap tube1 ! o!r cocks be+ almo/ wide op54 ,x might be ?\ght t ! m]cury w\ld t5d to pick up air 9 pass+ ?r\gh ! rubb] connections to ! fall tubes1 b ,i h n f\nd ?is to be ! case 9 practice4 ,!re is1 ( c\rse1 no difficulty 9 elim9at+ ! rubb] connections betwe5 ! fall tubes & ! m]cury supply f ! air trap1 b x impresses a great] rigidity on ! /ructure &1 z ,i say1 is n 9 g5]al necess>y4 ,x mu/ n be =gott5 t ! m]cury always ex]cises consid]able pressure on ! rubb] jo9ts1 & s !re is little t5d5cy = gas to come out ( ! rubb]4 ,! ?i/le funnels at ! head ( ! fall tubes provide a simple & excell5t means ( clean+ ! fall tubes4 ,= ?is purpose "s pure sulphuric acid :i* has be5 boil$ ) pure ammonium sulphate is plac$ 9 ea* ?i/le funnel1 & :5 ! fall tube is dirty ! connection to ! m]cury supply is cut (f at ! p9* cock s z to leave ! tube betwe5 ?is entry & ! head ( ! fall tube q full ( m]cury1 & ! sulphuric acid is all[$ to run d[n ! fall tube by rais+ ! /opp]4 ,! fall tube %\ld be all[$ to /& full ( acid = an h\r or s1 aft] :i* x w be f\nd to be fairly clean4 ,( c\rse ! m]cury res]voir ?us obta9s a lay] ( acid above ! m]cury1 & z x is bett] n to run ! risk ( any acid gett+ into ! pump except 9 ! fall tubes1 ! res]voir is be/ empti$ f ! bottom1 by a syphon1 if a suitable vessel _c be procur$1 s t clean m]cury only is )drawn4 ,! phosphorus p5toxide tube is be/ made z %[n simply f a bit ( wide tube1 ) two side connections fus$ to ! re/ ( ! pump4 ,x is no m tr\ble to cut ! tube & fuse x up aga9 :5 ! dry+ mat]ial is r5ew$ ?an to adju/ ! dry+ tube to two fix$ /opp]s1 :i* is ! alt]native4 ,! practice "h recomm5d$ is r5d]$ possible only by ! oxygas bl[-pipe ) hook$ nozzle4 ,! connection betwe5 ! pump & tube to be exhau/$ is made simply by a %ort bit ( rubb] tube imm]s$ 9 m]cury4 ,! phosphorus p5toxide %\ld be pure1 or r free f phosphorus & l[] oxides2 unless ?is be ! case1 ! vap\r aris+ f x is apt to soil ! m]cury 9 ! pump4 ,! phosphorus p5toxide is purifi$ by di/ill+ ) oxyg5 ov] r$-hot plat9um black2 if ?is _c be done1 ! p5toxide %\ld at lea/ be /rongly heat$ 9 a tube1 9 a curr5t ( dry air or oxyg51 be=e x is plac$ 9 ! dry+ tube4 ,! m]cury us$ = ! pump mu/ be scrupul\sly clean4 ,x does n1 h[ev]1 require to h be5 di/ill$ 9 vacuo4 ,x is suffici5t to purify x by all[+ x to fall 9 a f9e spray into a l>ge or r tall j> ( #be p] c5t nitric acid & #ge p] c5t wat]4 ,! m]cury is !n to be wa%$ & dri$ by heat+ to1 say1 #aaj ,c4 9 a porcela9 di%4 ,exhau/+ a ,ro5tg5 ,tube4 ,) a pump su* z has be5 describ$ !re is seldom any advantage 9 fus+ an extra connection to ! vacuum tube s z to all[ ( a prelim9>y exhau/ion by means ( a wat] pump4 ,ab\t half an h\r's pump+ may possibly be sav$ by mak+ use ( a wat] pump4 ,! tube to be exhau/$ is wa%$ & dri$ by c>eful heat+ ov] a ,buns5 burn] & by ! passage ( a curr5t ( air4 ,! exhau/+ tube is !n drawn d[n prep>atory to seal+ (f1 & ! app>atus plac$ ^u ! pump4 ,x is be/ held 9 position by a wood5 clamp support$ by a long retort /&4 ,exhau/ion may proce$ till ! m]cury 9 ! fall tubes comm5ces to hamm]4 ,at ?is po9t ! tube mu/ be c>efully heat$ by a ,buns5 flame1 ! temp]ature be+ br\ght up to1 say1 #djj ,c4 ,! heat+ may be cont9u$ int]mitt5tly till little or no effect due to ! heat+ is disc]nible at ! pump4 ,:5 ?is /age is rea*$1 or ev5 be=e1 ! electrodes may be connect$ up to ! coil & a dis*>ge s5t ?r\gh ! tube4 ,c>e mu/ be tak5 to /op ! dis*>ge z soon z a purple gl[ beg9s to appe>1 because :5 ?is happ5s1 ! resi/ance ( ! tube is v l[1 ! electrodes get v hot1 & may easily get damag$ by a p[]ful dis*>ge1 & ! plat9um ( ! anode 7if a focus tube is 9 "q7 beg9s to be di/ill$ on to ! glass4 ,! heat+ & sp>k+ are to be cont9u$ till ! resi/ance ( ! tube %>ply increases4 ,?is is te/$ by always hav+ a sp>k gap1 conv5i5tly =m$ by ! coil t]m9als1 9 p>allel ) ! tube4 ,if ! t]m9als are po9ts1 x is conv5i5t to set !m at ab\t "o qu>t] ( an in* di/ance ap>t4 ,z soon z sp>ks beg9 to pass betwe5 ! t]m9als ( ! sp>k gap x becomes necess>y to wat* ! process ( exhau/ion v c>efully4 ,9 ! fir/ place1 /op ! pump1 b let ! coil run1 & note :e!r ! sp>ks cont9ue to fl[ ov] ! t]m9als4 ,if ! glass & electrodes are gett+ gas free1 ! dis*>ge w cont9ue to pass by ! sp>k gap1 b if gas is /ill be+ freely giv5 (f1 !n 9 p]haps ?ree m9utes ! dis*>ge w return to ! tube1 & pump+ mu/ be recomm5c$4 ,! ,ro5tg5 effect only beg9s to appe> :5 ! tube has got to s high a /ate ( exhau/ion t ! resi/ance increases rapidly4 ,by pump+ & sp>k+1 ! resi/ance ( ! tube may be gradually rais$ till ! sp>k w\ld r jump ov] #b in*es ( air ?an g ?r\gh ! tube4 ,:5 ?is /ate is atta9$ ! ,ro5tg5 effect z te/$ by a scre5 ( calcium tung/ate %\ld be v brilliant4 ,no conclusion z to ! equival5t resi/ance ( ! tube c be arriv$ at s long z ! dis*>ge is kept go+ cont9ually4 ,:5 ! sp>k w\ld r g ov] an in* ( air 9 ! sp>k gap ?an ?r\gh ! tube ! pump+ & sp>k+ may be int]rupt$ & ! tube all[$ to re/ =1 say1 five m9utes4 ,x w g5]ally be f\nd t ! equival5t resi/ance ( ! tube w be l>gely increas$ by ?is p]iod ( quiesc5ce4 ,x may ev5 be f\nd t ! sp>k w n[ pref] to pass an air gap #c in*es long4 ,9 any case ! sp>k+ %\ld n[ be cont9u$1 ! pump be+ at re/1 & ! v>iations ( tube resi/ance wat*$ by adju/+ ! sp>k gap4 ,if ! resi/ance falls bel[ an equival5t ( #b in*es ( air 9 ! gap ! pump mu/ be br\ght into action aga9 & cont9u$ until ! resi/ance z ?us e/imat$ rema9s fairly con/ant =1 say1 t5 m9utes4 ,:5 ?is occurs ! n>r[ neck ( ! exhau/ tube may be /rongly heat$ till ! bl[-pipe flame beg9s to %[ traces ( sodium light4 ,! flame mu/ !n be )drawn & ! dis*>ge aga9 te/$4 ,?is is necess>y because x occasionally happ5s t gas is giv5 (f dur+ ! heat+ ( ! neck to ! neighb\rhood ( its fusion temp]ature4 ,if all is "r ! neck may n[ be fus$ entirely (f & ! tube is f9i%$4 ,tubes ( ! focus patt]n ) l>ge plat9um anodes are 9 g5]al 79 my exp]i5ce7 mu* m difficult to exhau/ ?an tubes ( ! k9d fir/ describ$4 ,?is is possibly to be attribut$ ma9ly to ! gas giv5 (f by ! plat9um1 b is also1 no d\bt1 due to ! tubes be+ mu* l>g] & expos+ a l>g] glass surface4 ,! type ( tube describ$ fir/ g5]ally takes ab\t two h\rs to exhau/ by a pump made z expla9$1 :ile a focus tube has tak5 z long z n9e h\rs1 eight ( :i* h be5 consum$ aft] ! tube 0 exhau/$ to ! hamm]+ po9t4 ,! pressure at :i* ! maximum heat+ ( ! anode by ! ca?ode rays occurs is a good deal high] ?an t at :i* ! maximum ,ro5tg5 effect is produc$4 ,!re is little d\bt t ! ,ro5tg5 radiation *anges 9 nature to "s ext5t z ! vacuum improves ei!r z a prim>y or second>y effect4 ,x is !re=e ( "s importance to te/ ! tube = ! purpose = :i* x is to be us$ dur+ ! actual exhau/ion4 ,x has be5 /at$1 = in/ance1 t ! relative p5etrability ( bone & fle% to ,ro5tg5 radiation atta9s a maximum diff]5ce at a c]ta9 pressure2 ?is is v likely ! case4 ,:e!r ?is effect is a direct function ( ! d5sity ( ! gas 9 ! tube1 or :e!r x is dep5d5t on ! voltage or "t integral ( ! curr5t dur+ ! dis*>ge1 are que/ions :i* /ill await a solution4 ,! prep>ation ( calcium tung/ate = fluoresc5t scre5s is v simple4 ,comm]cial sodium tung/ate is fus$ ) dri$ calcium *loride 9 ! proportion ( ?ree p>ts ( ! =m] to two p>ts ( ! latt]1 bo? con/itu5ts be+ 9 f9e p[d] & well mix$ toge!r4 ,! fusion is conduct$ 9 a ,flet*]'s crucible furnace 9 a clay crucible4 ,! temp]ature is rais$ z rapidly z possible to ! highe/ po9t :i* ! furnace w atta9--i4e4 a pure :ite heat4 ,at ?is temp]ature ! mixture ( salts becomes p>tly fluid1 or at lea/ pa/y1 & ! temp]ature may be kept at its highe/ po9t =1 say1 a qu>t] ( an h\r4 ,at ! end ( ?is "t ! mass is p\r$ & scrap$ on to a brick1 & :5 cold is brok5 up & boil$ ) a l>ge excess ( wat] to dissolve out all soluble matt]4 ,! insoluble "p1 :i* consi/s ( a gray %9+ p[d]1 is wa%$ sev]al times ) hot wat]1 & is f9ally dri$ on filt] pap] 9 a wat] ov54 ,9 ord] to prep>e a scre5 ! p[d] is gr\nd slightly ) v dilute %ellac v>ni%1 & is !n float$ ov] a glass plate s z to get an ev5 cov]+4 ,unless ! cov]+ be v ev5 ! scre5 is useless1 & no pa9s %\ld be sp>$ to secure ev5ness4 ,x is n exactly easy to get a regul> coat ( ! fluoresc5t mat]ial1 b x may be done ) a little c>e4 ,,*apt] ,,ii ,,glass-,,gr9d+ ,,& ,,opticians' ,,"w #eb4 ,z no in/ructions ( any practical value 9 ?is art h1 s f> z ,i "k1 appe>$ 9 any book 9 ,engli%1 ?\gh a great deal ( valuable in=mation has be5 giv5 9 ! ,engli% ,me*anic & else:]e1 ,i %all deal ) ! matt] suffici5tly fully = all practical purposes4 ,on ! o!r h&1 ,i d n propose to treat ( all ! me?ods :i* h be5 propos$1 b only ^? requisite = ! production ( ! results claim$4 ,! /ud5t is reque/$ to read ?r\gh ! *apt] be=e comm5c+ any p>ticul> op]ation4 #ec4 ,! simple/ way w be to describe ! process ( manufacture ( "s /&>d optical appliance1 f :i* a g5]al idea ( ! nature ( ! op]ations w be obta9$4 ,aft] ?is prelim9>y acc\nt special me?ods may be consid]$ 9 detail4 ,i w beg9 ) an acc\nt ( ! con/ruction ( an a*romatic object glass = a telescope1 n because a /ud5t 9 a physical laboratory w (t5 require to make "o1 b because x illu/rates ! usual processes v well2 & requires to be well & accurately made4 ,a k ( ! ord9>y pr9ciples ( optics on ! "p ( ! read] is assum$1 = !re are pl5ty ( books on ! !ory ( l5ses1 &1 9 any case1 x is my int5tion to treat ( ! art r ?an ( ! sci5ce ( ! subject4 ,by f> ! be/ %ort /atem5t ( ! pr9ciples involv$ :i* ,i h se5 is ,"l ,rayleigh's article on ,optics 9 ! ,encyclopa$ia ,britannica1 & ?is is amply suffici5t4 ,! fir/ "q t crops up is1 ( c\rse1 ! subject ( ! *oice ( glass4 ,x is obvi\s t ! glass mu/ be uni=m 9 refractive index ?r\gh\t1 & t x mu/ be free f air bubbles or bits ( opaque matt]4 ,footnote3 ,! complete te/+ ( glass = uni=mity ( refractive index c only be arriv$ at by gr9d+ & poli%+ a suffici5t portion ( ! surfaces to enable an exam9ation to be made ( e "p4 ,9 ! case ( a small disc x is suffici5t to poli% two or ?ree facets on ! edge1 & to exam9e ! glass 9 a field ( uni=m illum9ation ?r\gh ! w9d[s ?us =m$4 ,v slight irregul>ities w cause a mirage easily recognis$4 ,! simple/ proc$ure is to obta9 glass ( ! desir$ quality f ,messrs4 ,*ance ( ,birm+ham1 accord+ to ! foll[+ abbreviat$ li/ ( names & refractive indices1 :i* may be reli$ ^u3- ,d5sity4 ,refractive ,index4 ,c ,d ,f ,g ,h>d cr[n #b4he #a4eadf #a4eagb #a4ebcb #a4ebhj ,s(t cr[n #b4ee #a4eaai #a4eadf #a4ebaj #a4ebfc ,light fl9t #c4ba #a4egjj #a4egdj #a4ehci #a4eibb ,d5se fl9t #c4ff #a #fage #a4fbbd #a4fcdh #a4fdec ,extra d5se fl9t #c4he #a4fdej #a4fejd #a4ffdc #a4fgfa ,d\ble extra d5se fl9t #d4de #a4gjcf #a4gajc #a4gbgc 444 ,! above glasses may be _h 9 %eets f #j4be to #a in* ?ick1 & #f to #ab in*es squ>e1 at a co/ (1 say1 #gs4 #f;d4 p] p\nd4 ,discs c also be obta9$ ( any reasonable size4 ,discs #b in*es 9 diamet] co/ ab\t #a p] doz51 discs #c in*es 9 diamet] ab\t #ajs4 ea*4 ,! price ( discs increases enorm\sly ) ! size4 ,a #af-;in* disc w co/ ab\t #ajj4 ,= special purposes1 :]e ! desir$ quality ( glass does n appe> on ! li/1 an application may be made to ! ,j5a ,factory ( ,h]r ,s*ott4 ,9 ord] to give a def9ite example1 ,i may m5tion t = ord9>y telescopic objectives good results may be obta9$ by comb9+ ! h>d cr[n & d5se fl9t ( ,*ance's li/1 us+ ! cr[n to =m a d\ble convex1 & ! fl9t to =m a d\ble concave l5s4 ,! convex l5s is plac$ 9 ! m outw>d position 9 ! telescope1 i4e4 ! light passes fir/ ?r\gh x4 ,! conditions to be fulfill$ are3 7#a7 ,! glass mu/ be a*romatic2 7#b7 x mu/ h a small sph]ical ab]ration = rays conv]g+ to ! pr9cipal focus4 ,x is impossible to discuss ^! matt]s )\t go+ into a complete optical discussion4 ,! radii ( curvature ( ! surfaces1 beg9n+ ) ! fir/1 i4e4 ! ext]nal face ( ! convex l5s1 are 9 ! ratio ( #a1 #b1 & #c2 an all[ance ( #ae in*es focal l5g? p] in* ( ap]ture is reasonable 7see ,optics 9 ,ency4 ,brit471 & ! focal l5g? is ! same z ! greate/ radius ( curvature4 ,?us1 = an object glass #b in*es 9 diamet]1 ! fir/ surface ( ! convex l5s w\ld h a radius ( curvature ( #aj in*es1 ! surface common to ! convex & concave l5s w\ld h a radius ( curvature ( #bj in*es1 & ! la/ surface a radius ( curvature ( #cj in*es4 ,?is w\ld also be ab\t ! focal l5g? ( ! f9i%$ l5s4 ,! surfaces 9 contact h1 ( c\rse1 a common curvature1 & ne$ n be cem5t$ toge!r unless a slight loss ( light is inadmissible4 ,i w assume t a l5s ( ab\t #b in*es diamet] is to be made by h&1 i4e4 )\t ! help ( a special gr9d+ or poli%+ ma*9e2 ?is c be accompli%$ p]fectly well1 s long z ! diamet] ( ! glass is n above ab\t #f in*es1 aft] :i* ! lab\r is r too sev]e4 ,! two glass discs hav+ be5 obta9$ f ! mak]s1 x w be f\nd t !y are slightly l>g] 9 diamet] ?an ! quot$ size1 some?+ hav+ be5 left = ! wa/e ( work+4 ,x is difficult to deal ) ! processes ( l5s manufacture )\t ent]+ at e /age into r t$i\s details1 &1 :at is worse1 )\t int]rupt+ ! ma9 acc\nt = ! purpose ( describ+ subsidi>y in/rum5ts or processes4 ,9 ord] t ! read] may h "s guide 9 ?read+ ! maze1 x is necess>y t he %\ld comm5ce ) a cle> idea ( ! broad pr9ciples ( con/ruction :i* are to be c>ri$ out4 ,= ?is purpose x seems desirable to beg9 by r\ghly indicat+ ! v>i\s /eps :i* are to be tak54 7#a7 ,! glass is to be made circul> 9 =m & ( a giv5 diamet]4 7#b7 ,call$ ,r\gh ,gr9d+4 ,! surfaces ( ! glass are to be made r\ghly convex1 plane1 or concave1 z may be requir$2 ! glass is to be equally ?ick all r\nd ! edge4 ,9 ?is process ! glass is abrad$ by ! use ( s& or em]y rubb$ ov] x by prop]ly %ap$ pieces ( iron or lead call$ tools4 7#c7 ,! glass is gr\nd ) em]y to ! correct sph]ical figure z giv5 by a sph]omet]4 7#d7 ,call$ ,f9e ,gr9d+4 ,! /ate ( ! surface is gradually improv$ by gr9d+ ) f9] & f9] grades ( em]y4 7#e7 ,! glass is poli%$ by r\ge4 7#f7 ,! glass is figur$4 ,?is means t x is gradually alt]$ 9 =m by a poli%+ tool till x gives ! be/ results z f\nd by trial4 ,9 processes #b to #e c\nt]p>t tool surfaces are requir$--z a rule two convex & two concave surfaces = ea* l5s surface4 ,^! subsidi>y surfaces are work$ 7i4e4 gr\nd7 on discs ( ca/ iron fac$ ) glass1 or on slate discs2 & discs ?us prep>$ are call$ tools4 ,tak+ ^! processes 9 ! ord] nam$1 ! mode ( manufacture is %ortly z foll[s3- 7#a7 ,! disc ( glass1 obta9$ 9 a r\ghly circul> =m1 is m\nt$ on an ord9>y la!1 be+ conv5i5tly cem5t$ by ,regnault's ma/ic to a small face plate4 ,! la! is rotat$ sl[ly1 & ! glass is gradually turn$ d[n to a circul> figure by means 7#a7 ( a tool ) a diamond po9t2 or 7#b7 an ord9>y h&-file moi/5$ ) k]os5e1 z describ$ 9 #db2 or 7#c7 a mass ( brass or iron s]v$ ) a mixture ( em]y--or s&--& wat] f$ on to ! disc1 s t ! disc is gradually gr\nd circul>4 ,! op]ation ( mak+ a circul> disc ( giv5 diamet] does n diff] 9 any important p>ticul> f ! simil> op]ation 9 ! case ( brass or iron1 & is 9 fact m]ely a matt] ( turn+ at a sl[ spe$4 7#b & #c7 ,r\gh+ or br++ ! surfaces ( ! glass r\ghly to ! prop] convex or concave %ape4 ,?is is accompli%$ by gr9d+1 g5]ally ) s& 9 l>ge works1 or ) em]y 9 ! laboratory1 :]e ! "t sav$ is ( m importance ?an ! value ( ! em]y4 ,discs ( iron or brass are ca/ & turn$ s z to h a diamet] slightly less ?an t ( ! glass to be gr\nd1 & are1 say1 half an in* ?ick4 ,^! discs are turn$ convex or concave on "o face accord+ z !y are to be employ$ 9 ! production ( concave or convex glass surfaces4 ,! prop] degree ( convexity or concavity may be approximat$ to by turn+ ) ord9>y turn+ tools1 us+ a circul> arc cut f z9c or glass 7z w be describ$7 z a template or patt]n4 ,?is also is a m]e matt] ( turn+4 ,! fir/ approximation to ! desir$ convex or concave surface ( ! glass is atta9$ 79 ! case ( small l5ses1 say up to ?ree in*es diamet]7 by rotat+ ! glass on ! la! z describ$ above 7= ! purpose ( giv+ x a circul> edge7 & hold+ ! tool aga9/ ! rotat+ glass1 a pl5tiful supply ( co>se em]y & wat]1 or s& & wat]1 be+ suppli$ betwe5 ! glass & metal surfaces4 ,! tool is held by h& aga9/ ! surface ( ! revolv+ glass1 & is con/antly mov$ ab\t1 bo? r\nd its own axis ( figure & to & fro across ! glass surface4 ,9 ?is way ! glass gradually gets convex or concave4 ,! curvature is te/$ f "t to "t by a sph]omet]1 & ! tool is increas$ or decreas$ 9 curvature by turn+ x on a la! s z to cause x to gr9d ! glass m at ! edges or 9 ! middle accord+ to ! indications ( ! sph]omet]4 ,?is in/rum5t1 by ! way--s important = l5s mak]s--consi/s ess5tially ( a k9d ( ?ree-legg$ /ool1 ) an additional leg plac$ at ! c5tre ( ! circle circumscrib+ ! o!r ?ree4 ,?is c5tral leg is 9 reality a f9e screw ) a v l>ge head graduat$ on ! edge1 s t x is easy to compute ! fractions ( a turn giv5 to ! screw4 ,! in/rum5t is fir/ plac$ on a flat plate1 & ! c5tral screw turn$ till its end j t\*es ! plate1 a /ate ( affairs :i* is v %>ply disc]nible by ! slight rock+ :i* x enables ! in/rum5t to und]go :5 pu%$ by ! h&4 ,see ! sket*4 ,on a convex or concave surface ! screw has to be screw$ 9 or out1 & f ! am\nt ( screw+ necess>y to br+ all f\r po9ts into equal contact1 ! curvature may be asc]ta9$4 ,let a be ! di/ance betwe5 ! equidi/ant feet1 & d ! di/ance ?r\gh :i* ! screw is protrud$ or retract$ f its z]o position on a flat surface4 ,!n ! radius ( curvature rho is giv5 by ! =mula #brho a#b_/c;d d4 ,fig4 #dc4 ,! process ( r\gh+ is n always c>ri$ out exactly z describ$1 & w be ref]r$ to aga94 7#d7 ,! glass be+ approximately ( ! prop] radius ( curvature on "o side1 x is rev]s$ on ! *uck & ! same process gone ?r\gh on ! o!r side4 ,aft] ?is ! glass is usually dism\nt$ f ! la! & m\nt$ by cem5t on a p$e/al1 :i* is m]ely a wood5 /& ) a heavy foot1 s t ! glass may be held conv5i5tly = ! workman4 ,sometimes a p$e/al ab\t f\r feet high is fix$ 9 ! floor ( ! room1 s t ! workman engag$ 9 gr9d+ ! l5s may walk r\nd & r\nd x to secure uni=mity4 ,= ord9>y purposes1 h[ev]1 a %ort p$e/al may be plac$ on a table & rotat$ f "t to "t by h&1 ! op]ator sitt+ d[n to 8 "w4 ,r\gh iron or brass tools d n succe$ = f9e gr9d+--i4e4 gr9d+ ) f9e em]y1 because p>ticles ( em]y become emb$d$ 9 ! metal s tightly t !y _c be got out by any ord9>y clean+4 ,if we h be5 us+ em]y pass+ say a sieve ) #fj ?reads to ! in*1 & !n g on to "s pass+ say #ajj ?reads to ! in*1 a few ( ! co>s] p>ticles w adh]e to ! tool1 & g on cutt+ & scrat*+ all ! "t gr9d+ by means ( ! f9] em]y is 9 progress4 ,to get ov] ?is x is usual to use a r diff]5t k9d ( gr9d+ tool4 ,a v good k9d is made by cem5t+ small squ>es ( glass 7say up to half an in* on ! side71 on to a disc ( slate slightly small] ?an ! l5s surface to be =m$ 7,fig4 #ea74 ,! glass-slate tool is !n r\gh$ j l ! l5s surface1 b1 ( c\rse1 if ! l5s has be5 r\gh$ convex ! tool mu/ be r\gh$ concave4 ,! r\gh$ tool is !n us$ to gradually improve ! f95ess ( gr9d+ ( ! glass4 ,= ?is purpose gr9d+ by h& is resort$ to1 ! tool & l5s be+ suppli$ cont9ually ) f9] & f9] em]y4 ,fig4 #eb gives an idea ( ! way 9 :i* ! tool is mov$ across ! glass surface4 ,v little pressure is requir$4 ,! tool is c>ri$ 9 small circul> sweeps r\nd & r\nd ! l5s1 s t ! c5tre ( ! tool describes a _m-loop$ curve on ! l5s surface4 ,! tool mu/ be all[$ to rotate ab\t its own axis2 & ! l5s & p$e/al mu/ also be rotat$ f "t to "t4 ,e few m9utes ! circul> /rokes are int]rupt$1 & simple1 /raight1 transv]se /rokes tak54 ,9 no case 7except to correct a1 defect1 z w be expla9$7 %\ld ! tool ov]hang ! l5s surface by m ?an ab\t "o qu>t] ! diamet] ( ! latt]4 ,aft] gr9d+ say = an h\r ) "o size ( em]y f$ 9 by means ( a clean /ick say e five m9utes1 ! em]y is wa%$ (f1 & ev]y?+ c>efully clean$4 ,! process is !n repeat$ ) f9] em]y1 & s on4 ,! diff]5t grades ( em]y are prep>$ by tak+ advantage ( ! fact t ! small] ! p>ticles ! long] d !y rema9 susp5d$ 9 wat]4 ,"s em]y mud f a r\gh+ op]ation is /irr$ up ) pl5ty ( wat] & left a few seconds to settle1 ! liquor is !n decant$ to a second jug & left say = d\ble ! "t1 say t5 seconds2 x is decant$ aga91 & s on till f\r or five grades ( em]y h be5 accumulat$1 ea* jug conta9+ f9] em]y ?an its pr$ecessor 9 ! process4 ,x is n mu* use us+ em]y :i* takes m ?an half an h\r to settle 9 an ord9>y b$room jug4 ,:at rema9s 9 ! liquid to be decant$ is mo/ly glass mud & n em]y at all4 ,! process ( f9e gr9d+ is cont9ually *eck$ by ! sph]omet]1 & ! art consi/s 9 kn[+ h[ to move ! gr9d+ tool s z to make ! l5s surface m or less curv$4 ,9 g5]al x may be said t if ! tool is mov$ 9 small sweeps1 & n all[$ to ov]hang mu*1 ! ,c5tre ( ! l5s w be m abrad$1 :ile if bold free /rokes are tak5 ) mu* ov]hang+1 ! edges ( ! l5s w be m gr\nd away4 ,by ! ex]cise ( pati5ce & p]sev]ance any "o w succe$ 9 gradually f9e gr9d+ ! l5s surface & keep+ x to ! sph]omet]1 b ! skill comes 9 do+ ?is rapidly by v>y+ ! %ape ( ! /rokes be=e any appreciable alt]ation ( curvature has come ab\t4 ,poli%+4 ,! mo/ simple way ( poli%+ is to coat ! gr9d+ tool ) pap]1 z w be describ$1 & !n to bru% "s r\ge into ! pap]4 ,! poli%] is mov$ ov] ! "w 9 mu* ! same way z ! f9e gr9d+ tool1 until ! glass is poli%$4 ,_m op]ators pref] to use a tool made by squeez+ a disc ( slate1 arm$ ) squ>es ( w>m pit*1 aga9/ ! l5s surface 7f9ely gr\nd71 & !n cov]+ ^! squ>es ) r\ge & wat] in/ead ( em]y & wat] z 9 ! f9e gr9d+ process4 ,! f9al process is call$ figur+4 ,x w 9 g5]al be unnecess>y ) a small l5s4 ,) l>ge l5ses or mirrors ! f9al t\*es h to be giv5 aft] ! optical behavi\r ( ! l5s or mirror has be5 te/$ ) ! telescope itself1 & ?is process is call$ figur+4 ,a book might easily be writt5 on ! optical indications ( v>i\s imp]fections 9 a mirror or l5s4 ,suffice x to say "h t a suffici5tly skill$ p]son w be able to decide f an obs]vation ( ! behavi\r ( a telescope :e!r a l5s w be improv$ by alt]+ ! curvature ( "o or all ( ! surfaces4 ,a v small alt]ation w make a l>ge diff]5ce 9 ! optical prop]ties1 s t 9 g5]al figur+ is done m]ely by us+ ! r\ge poli%+ tool z an abrad+ tool1 & caus+ x to alt] ! curves 9 ! mann] already sugge/$ = gr9d+4 ,!re are o!r me?ods bas$ on knock+ squ>es out ( ! pit*-poli%] s t "s p>ts ( ! glass may be m abrad$ ?an o!rs4 ,! figur+ & poli%+ may be done by h& j l ! gr9d+4 ,!re are ma*9es1 h[ev]1 :i* c be made to execute ! prop] motions1 & a poli%] is set 9 su* a ma*9e1 & ! me*anical "w done is by no means inconsid]able4 ,9 fact = surfaces above six in*es 9 diamet] few p are /rong en\gh to "w a poli%] by h& ow+ to ! int5se adhesion betwe5 x & ! exactly fitt+ glass surface4 ,su* is a g5]al outl9e ( ! processes requir$ to produce a l5s or mirror4 ,^! processes w n[ be dealt ) 9 mu* great] detail1 & a c]ta9 am\nt ( repetition ( ! above w un=tunately be necess>y3 ! read] is ask$ to p>don ?is4 ,x w also be advisable = ! read] to beg9 by read+ ! :ole acc\nt be=e he comm5ces any p>ticul> op]ation4 ,! reason = ?is is t x has be5 desirable to keep to ! ma9 acc\nt z f> z possible )\t ins]t+ special in/ructions = subsidi>y op]ations1 h[ev] important !y may be2 consequ5tly x may n always be q cle> h[ ! /eps describ$ are to be p]=m$4 ,x w be f\nd1 h[ev]1 t all necess>y in=mation is really giv51 ?\gh p]haps n always exactly 9 ! place ! read] might at fir/ expect4 #ed4 ,all ! discs t ,i h se51 come f ! mak]s already r\ghly gr\nd on ! edges to a circul> figure--b occasionally ! figure is v r\gh inde$--& 9 "s cases1 especially if small l5ses h to be made1 x is conv5i5t to beg9 by cutt+ ! glass discs out ( glass %eet1 :i* also may be pur*as$ ( suit-able glass4 ,to d ?is1 ! simple/ way is to beg9 by cutt+ squ>es & !n cutt+ (f ! corn]s ) ! diamond1 ! approximate circul> figure be+ obta9$ by gr9d+ ! edges on an ord9>y gr9d/one4 ,if ! pieces are l>g]1 "t & mat]ial may be sav$ by us+ a diamond compass1 i4e4 an ord9>y draw+ compass arm$ ) a diamond to cut circles on ! glass1 & break+ ! sup]flu\s glass away by means ( a pair ( spectacle-mak]'s %anks 7,fig4 #dd71 or :at does equally well1 a pair ( pli]s ) s(t iron jaws4 ,) ^! in/rum5ts glass c be *ipp$ gradually up to any l9e1 :e!r diamond-cut or n1 ! jaws ( ! p9c]s be+ work$ aga9/ ! edge ( ! glass1 s z to gradually cru% x away4 ,fig4 #dd4 ,assum+ t ! glass has be5 b\ght or made r\ghly circul>1 x mu/ be f9i%$ on ! la!4 ,= ?is purpose x is necess>y to *uck x on an iron or h>dwood *uck1 z %[n 9 ,fig4 #df4 ,= a l5s bel[ say an in* 9 diamet]1 ! c5t]+ cem5t may be us$2 b = a l5s ( a diamet] great] ?an ?is1 suffici5t adhesion is easily obta9$ ) ,regnault's ma/ic1 & its l[ melt+ po9t gives x a decid$ advantage ov] ! %ellac composition4 ,! glass may be heat$ gradually by plac+ x on ! wat] ba?1 or actually 9 ! wat]1 & gradually br++ ! wat] up to ! boil+-po9t4 ,! glass1 be+ tak5 out1 is rapidly wip$1 & rubb$ ) a bit ( wa/e moi/5$1 n wet1 ) a little turp5t9e3 its surface is !n rubb$ ) a /ick ( ma/ic previ\sly w>m$ s z to melt easily4 ,! surface ( ! *uck be+ also w>m1 & cov]$ ) a lay] ( melt$ cem5t1 x is appli$ to ! glass4 ,! la! is turn$ sl[ly by h&1 & ! glass pu%$ gradually into ! mo/ c5tral position2 x is !n press$ tight aga9/ ! *uck by ! back re/1 a bit ( wood be+ int]pos$ = obvi\s reasons4 ,:5 all is cold ! turn+ may be proce$$ )4 ,! quicke/ way is to use ! me?od already describ$ 7i4e4 actual turn+ by a file tool72 b if ! /ud5t pref]s 7"t be+ no object71 he may accompli% ! r$uction to a circul> =m v easily by gr9d+4 ,fig4 #de4 ,fig4 #df4 ,= ?is purpose he w require to make ! foll[+ arrangem5ts 7,fig4 #de74 ,if ! la! has a slide re/1 a piece ( /\t iron may be b5t & cut s z to fit ! tool re/1 & project b5ea? ! glass4 ,! iron mu/ be fairly rigid1 = if x spr+s appreciably b5ea? ! pressure ( ! glass1 x w n gr9d ! latt] really r\nd4 ,! la! may run r fa/] ?an = turn+ ca/ iron ( ! same size4 ,co>se em]y1 pass+ ?r\gh a sieve ( #hj ?reads to ! in* 7run71 may be f$ 9 betwe5 ! glass & iron1 & ! latt] screw$ up till ! disc j gr9ds slightly z x goes r\nd4 ,a beg9n] w g5]ally 79 ?is z 9 all cases ( gr9d+ processes7 t5d to fe$ too fa/--no gr9d+ process c be hurri$4 ,if a slide re/ is n available1 a h+$ bo>d1 c>ry+ a bit ( iron1 may 7see ,fig4 #de7 be arrang$ s z to turn ab\t its h+e at ! back ( ! la!2 & x may be screw$ up readily en\gh by pass+ a long set-screw ?r\gh ! front edge1 s t ! po9t ( ! screw be>s ^u ! la! b$4 ,i may add t em]y behaves z if x 7 greasy1 & x is difficult to wet x ) clean wat]4 ,?is is easily got ov] by add+ a little soap or alcohol to ! wat]1 or ex]cis+ a little pati5ce4 ,a good supply ( em]y & wat] %\ld be kept betwe5 ! disc & ! iron2 a little putty may be arrang$ r\nd ! po9t ( contact on ! iron to =m a tempor>y tr\gh4 ,9 any case ! result+ em]y mud %\ld on no acc\nt be ?r[n away1 b %\ld be c>efully kept = fur!r use4 ,! process is complete :5 ! glass is p]fectly r\nd & ( ! requir$ diamet] z te/$ by callip]s4 #ee4 ,! next /ep is to r\gh out ! l5s1 & ?is may easily be done by rotat+ x m sl[ly1 i4e4 ) a surface spe$ ( t5 feet p] m9ute1 & turn+ ! glass ) a h>d file1 z expla9$ 9 #db4 ,if x is desir$ to employ ! slide re/1 x is quick] & bett] to use a diamond tool--an in/rum5t q readily made1 & ( great s]vice = turn+ em]y :eels & ! l1--a ?+1 9 fact1 :i* no work%op %\ld be )\t4 ,a bit ( diamond bort1 or ev5 a cle> ?\gh (f-col\r /one1 may be employ$4 ,an ord9>y la! tool is prep>$ by draw+ d[n ! tool /eel to a long cone1 resembl+ ! ord9>y practice 9 prep>+ a bor+ tool4 ,! apex ( ! cone mu/ be cut (f till x is only slightly l>g] ?an ! greate/ transv]se diamet] ( ! diamond spl9t]4 ,! latt] may h almo/ any %ape--a triangul> po9t1 "o side ( a ?ree-sid$ prism is v conv5i5t4 ,a hole is drill$ 9 ! /eel 7:i* mu/ h be5 well s(t5$71 only j l>ge en\gh to all[ ! diamond to ent]--if ! spl9t] is ?ick] 9 ! middle ?an at ei!r end1 s mu* ! bett]--! diamond is fa/5$ 9 position by squeez+ ! s(t /eel walls tightly d[n ^u x4 ,p]sonally ,i pref] to use a tool hold]1 & 9 ?is case g5]ally m\nt ! diamond 9 a bit ( brass rod ( ! prop] diamet]2 & in/ead ( p9*+ 9 ! sides ( ! cavity1 ,i t9 !m1 & set ! diamond 9 position ) a drop ( s(t sold]4 ,fig4 #dg4 ,9 pur*as+ diamond bort1 a good plan is to buy fragm5ts t h be5 employ$ 9 diamond drill+1 & h become too small to reset2 9 ?is case "s idea z to ! h>dness ( ! bits may be obta9$4 ,full details z to diamond tool-mak+ are giv5 9 books on wat*-mak+1 & 9 ,holtzapffell's great "w on ,me*anical ,manipulation2 b ! above notes are all t are really necess>y--x is1 9 fact1 a v simple matt]4 ,! only advantage ( us+ a diamond tool = glass turn+ is t "o does n ne$ to be always tak+ x out ( ! re/ to %>p5 x1 :i* g5]ally happ5s ) h>d /eel1 especially if ! "w is turn$ a little too fa/4 ,i recomm5d1 !re=e1 t ! /ud5t %\ld boldly g to "w free h& ) a h>d file2 b if he pref] ! m =mal me?od1 or di/ru/ 8 skill 7:i* he %\ld n d71 !n let him use a diamond po9t1 ev5 if he has ! tr\ble ( mak+ x4 ,:5 us+ a diamond x is n necess>y to employ a lubricant1 b !re is "s advantage 9 do+ s4 ,! surface ( ! l5s c be r\ghly %ap$ by turn+ to a template or patt]n made by cutt+ a circul> arc 7( ! same radius z ! requir$ surface7 out ( a bit ( %eet z9c4 ,ano!r v h&y way ( mak+ templates ( great accuracy is to use a beam compass 7con/ruct$ f a light wood5 b>7 ) a glazi]'s diamond in/ead ( a p5cil4 ,a bit ( ?9 %eet glass is cut across ) ?is compass to ! prop] curvature--:i* c be done ) consid]able accuracy & ! two halves ( ! plate1 aft] break+ along ! cut1 are gr\nd toge!r ) a view to avoid+ slight local irregul>ities1 by means ( a little f9e em]y & wat] laid betwe5 ! edges4 ,9 ?is process ! glass is conv5i5tly support$ on a clean bo>d or slate1 & ! bits are rubb$ backw>ds & =w>ds aga9/ ea* o!r4 #ef4 ,x is n v easy = a beg9n] to turn a bit ( any?+--iron1 wood1 or glass--) great accuracy to fit a template1 & consequ5tly "t may be sav$ by ! foll[+ proc$ure1 appli$ z soon z ! figure ( ! template is r\ghly obta9$4 ,a disc ( lead or iron1 ( ! same diamet] z ! glass1 & ( approximately ! prop] curvature1 is prep>$ by turn+1 & is arm$ ) a h&le project+ coaxially f ! back ( ! disc4 ,! glass revolv+ ) mod]ate spe$ on ! la!1 ! lead tool1 suppli$ ) co>se em]y & wat]1 is held aga9/ x1 c>e be+ tak5 to rotate ! tool by ! h&le1 & also to move x backw>ds & =w>ds across ! disc1 ?r\gh a di/ance1 say1 up to half an in*2 if x is all[$ to ov]hang too mu* ! edges ( ! glass disc w be ov]gr\nd4 ,by ! use ( su* a tool ! glass c readily be br\ght up to ! template4 ,! only ?+ t rema9s1 s f> z ! description ( ?is "p ( ! process goes1 is to give a note or two z to ! be/ way ( mak+ ! lead tools1 & = ?is purpose ! ma9 n>rative ( processes mu/ be int]rupt$4 ,! easie/ way is to make a set ( discs to beg9 )4 ,= ?is purpose take ! m&rel out ( ! la!1 & place x nose d[nw>ds 9 ! c5tre ( an iron r+ ( prop] diamet] on a flat & level iron plate4 ,! discs are made by p\r+ lead r\nd ! screw-nose ( ! m&rel4 ,?is me?od1 ( c\rse1 leaves !m ) a hole 9 ! c5tre2 b ?is c be /opp$ up by plac+ ! hot disc 7f :i* ! m&rel has be5 unscrew$7 on a hot plate1 & p\r+ 9 a suffici5cy ( v hot lead2 or1 bett] /ill1 ! m&rel c be support$ v]tically at any desir$ di/ance above ! plate :ile ! ca/+ is be+ p\r$4 ,lead discs prep>$ 9 ?is way are easily turn$ s z to =m v conv5i5t *ucks = brass "w1 & = use 9 ! case n[ be+ treat$1 !y are easily turn$ to a template1 us+ woodturn]s' tools1 :i* "w bett] if oil$1 & mu/ be set to cut1 n scrape4 ,if ! op]ator does n m9d ! tr\ble ( cutt+ a screw1 or if he has a jaw *uck1 ! lead may be replac$ by iron ) "s advantage4 ,! foll[+ is a neat way ( mak+ concave tools4 ,x is an application ( ! pr9ciple ( hav+ ! cutt+ tool z long z ! radius ( curvature1 & all[+ x to move ab\t ! c5tre ( curvature4 ,place ! disc ( iron or lead on ! la! m&rel or 9 ! *uck1 & set ! slide re/ s t x is free to slide up or d[n ! la! b$4 ,take a b> ( tool /eel & cut x a little long] ?an ! radius ( curvature requir$4 ,=ge & f9i% "o end ( ! b> into a po9t$ turn+ tool ( ! ord9>y k9d4 ,measure ! radius ( curvature f ! po9t ( ! tool along ! b>1 & bore a hole1 ^: c5tre is at ?is po9t1 ?r\gh ! b> f ! upp] to ! l[] face4 ,i reg>d ! upp] face z ! "o ^: horizontal plane conta9s ! cutt+ po9t :5 ! tool is 9 use4 ,clamp a tempor>y back c5tre to ! la! b$1 & let x c>ry a p9 9 ! v]tical plane ?r\gh ! la! c5tres1 & let ?is p9 exactly fit ! hole 9 ! b>4 ,fig4 #dh4 ,place ! radius tool 9 position = cutt+1 & let x be lightly held 9 ! slide re/ ne>ly at ! cutt+ po9t1 ! c5tre ( rotation ( ! p$e/al 7or its equival5t7 pass+ ?r\gh ! c5tral l9e ( ! b>4 ,!n adju/ ! tempor>y back re/1 s t ! tool w take a cut4 ,9 ! sket* ! tool is %[n sw++ ab\t ! back c5tre in/ead ( ab\t a p9--!re is little to *oose betwe5 ! me?ods unless economy ( tool /eel is an object4 ,! tool mu/ n[ be f$ across ! "w4 ,! p$e/al mu/ ( c\rse be free to rotate1 & ! slide re/ to slip up & d[n ! b$4 ,9 ?is way a bett] concave gr9d+ tool c be made ?an w\ld be made by a beg9n] by turn+ to a template--?\gh an exp]t turn] w\ld probably c>ry out ! latt] op]ation s z to obta9 an' accuracy ( ! same ord]1 & w\ld c]ta9ly d x 9 mu* less "t ?an w\ld be requir$ 9 sett+ up ! special arrangem5ts "h describ$4 ,on ! o!r h&1 if sev]al surfaces h to be prep>$1 z 9 ! mak+ ( an a*romatic l5s1 ! quicke/ way w\ld be by ! use ( ! radius tool1 bor$ ( c\rse to "w at ! sev]al radii requir$4 ,i h tri$ bo? me?ods1 & my *oice w\ld dep5d p>tly on ! la! at my disposal1 & p>tly on ! numb] ( gr9d+ tools t _h to be prep>$4 ,hav+ obta9$ a concave tool ( any giv5 radius1 x is easily copi$--negatively1 s z to make a convex tool 9 ! foll[+ mann]4 ,adju/ ! concave tool already made on ! back re/1 s t if x rotat$ ab\t ! l9e ( c5tres1 x w\ld rotate ab\t its axis ( figure4 ,arrangem5ts = ?is c easily be made1 b ( c\rse !y w dep5d on ! detail$ /ructure ( ! la!4 ,use ! slide re/ z be=e1 i4e4 let x grasp an ord9>y turn+ tool lightly1 ! p$e/al be+ fix$1 b ! re/ free to slide up or d[n ! la! b$4 ,pu% ! back re/ up till ! butt ( ! turn+ tool 7gr\nd to a r\nd$ po9t7 re/s aga9/ ! concave gr9d+ tool4 ,if ! diamet] ( ! convex tool requir$ be v small comp>$ ) ! radius ( curvature ( ! surface 7! mo/ usual case71 x is only necess>y to fe$ ! cutt+ tool across to copy ! concave surface suffici5tly ne>ly4 ,fig4 #di4 ,!re seems no reason1 h[ev]1 :y ^! me?ods %\ld n be appli$ at once to ! glass disc by means ( a diamond po9t1 & ! r\gh gr9d+ ?us entirely avoid$4 ,i am in=m$ t ?is has be5 done by ,sir ,h5ry ,bessem]1 b t ! me?od 0 f\nd to pres5t no great advantage 9 practice4 ,a read] ) a ta/e = me*anical exp]im5t+ might try radius b> tools ) small c>borundum :eels rapidly driv5 in/ead ( a diamond4 ,en\gh has n[ be5 said to enable any "o to prep>e r\gh convex or concave gr9d+ tools ( iron or lead1 & ( ! same diamet] z ! glass to be gr\nd4 ,! g5]al effect ( ! process ( r\gh+ ! rotat+ l5s surface is to alt] ! radius ( curvature ( bo? tool & glass2 h5ce x is necess>y to h = ea* gr9d+ tool ano!r to fit x1 & enable x to be kept 7by work+ ! two toge!r7 at a con/ant figure4 ,aft] a little practice x w be f\nd possible to br+ ! glass exactly up to ! requir$ curvature z te/$ by template or sph]omet]4 ,! art ( ! process consi/s 9 alt]+ ! %ape ( ! gr9d+ tool s z to take (f ! glass :]e requir$1 z describ$ 9 #ec1 & f ?is po9t ( view lead has "s advantages2 7op9ions v>y z to ! relative advantages ( lead & iron tools = ?is purpose1 h[ev]74 ,! subsidi>y gr9d+ tool is n actually ne$$ = ?is prelim9>y op]ation1 b x has to be made "s "t ) a view to fur!r proc$ure1 & occasionally is ( s]vice "h4 #eg4 ',! glass disc mu/ be gr\nd approximately to ! prop] curvature on ea* side be=e any f9e gr9d+ is comm5c$4 ,x is precisely = ?is purpose t ! previ\s turn+ ( ! disc is recomm5d$1 = x is easy to unm\nt & rec5tre a r\nd object1 b n s easy if ! object h an indef9ite %ape4 ,us+ a cem5t :i* is pla/ic be=e x sets1 ! disc may be easily tak5 (f ! *uck & c5tr$ by a little h&icraft1 i4e4 by rotat+ ! la! sl[ly & pu%+ ! disc into su* a position t x rotates ab\t its axis4 ,! gr9d+ ( ! second surface is accompli%$ exactly z 9 ! =m] case2 ( c\rse on rev]s+ ! glass ! *uck has to be slightly turn$ up to fit ! convex or concave surface4 #eh4 ,!re is1 h[ev]1 "o po9t ( int]e/ & importance--att5tion to :i* w save a good deal ( useless lab\r aft]w>ds4 ,! glass mu/ be gr\nd 9 su* a mann] t ! ?ickness at ! edge is ! same all r\nd4 ,9 o!r words1 ! axes ( figure ( ! two surfaces mu/ co9cide4 ,?is w be ! case if ! rec5t]+ has be5 accurately p]=m$1 & !re=e no pa9s %\ld be sp>$ to see t x is exactly c>ri$ out4 ,any simple =m ( v]ni] gauge 7su* z ,br[n & ,%>pe's v]ni] callip]s7 w s]ve to all[ ( a suffici5tly accurate measurem5t ( ! edge ?ickness ( ! l5s4 ,if any diff]5ce ( ?ickness is obs]v$ z ! gauge moves r\nd ! edge1 "o or o!r ( ! surfaces mu/ be regr\nd4 ,( c\rse ! latitude ( error :i* may be p]mitt$ dep5ds s mu* on ! f9al arrangem5ts = a special f9i%+ process call$ ! c5t]+ ( ! l5s--:i* w be describ$--t x is difficult to fix a limit1 b p]haps "o-?\s&? ( an in* may be m5tion$ z a suitable am\nt = a #b-;in* disc4 ,= r\gh "w1 ( c\rse2 m m>g9 may be admitt$4 #ei4 ,9 a l>ge %op ,i imag9e t l5ses ( only two in*es diamet] w\ld be gr\nd 9 ne/s2 or1 9 o!r words1 a numb] w\ld be work$ at a "t1 & c5t]+1 ev5 ( a r\gh k9d1 w\ld be left to ! la/2 b ?is process w be treat$ h]eaft]4 ,at pres5t ,i %all assume t only "o l5s w be made at a "t4 ,consequ5tly we n[ ent] on ! /age ( f9e gr9d+ by h&4 ,a lead5 p$e/al1 = ! sake ( /ability1 mu/ be provid$ on :i* to m\nt ! l5s1 s t ! surface to be op]at$ on may be ne>ly horizontal 7,fig4 #ej74 ,be=e ?is c be done1 h[ev]1 fre% gr9d+ tools 7two = ea* surface7 mu/ be prop]ly prep>$4 ,aft] try+ sev]al plans ,i unhesitat+ly recomm5d t all f9e-gr9d+ surfaces %\ld be made ( glass4 ,?is is easily done by tak+ two discs ( lead1 or iron1 or slate1 cut to a "o-t5? in* small] radius ( curvature 79 ! case ( a convex tool1 & ! opposite 9 ! o!r case7 ?an ! l5s surface 7,fig4 #ea1 ,a74 ,on ^!1 squ>e bits ( %eet glass1 "o-t5? ( an in* ?ick1 are to be cem5t$1 s z to leave *annels ( ab\t "o-eigh? ( an in* betwe5 ea* bit ( glass 7,fig4 #eb1 ,b74 ,! ma/ic cem5t =m]ly describ$ may be employ$ = ?is purpose4 ,fig4 #ej4 ,! bits ( glass ought fir/ to h _! edges dress$ smoo? on ! gr9d-/one4 ,a convex & concave glass surface hav+ be5 ?us r\ghly prep>$1 !y mu/ be m\nt$ 9 turn 9 ! la!1 & br\ght to ! prop] curvature by gr9d+ ) ! tools =m]ly employ$ & te/$ by ! template or sph]omet]4 ,x is well to control ?is process by means ( a sph]omet]1 s t ! desir$ radius may be approximately rea*$4 ,! two glass-gr9d+ tools are !n gr\nd toge!r by h& 7see #ec & #fa71 ! sph]omet] be+ employ$ f "t to "t to *eck ! progress ( ! "w4 ,9 g5]al1 if l>ge circul> sweeps are tak51 greatly ov]hang+ ! side ( ! glass surface to be figur$1 bo? ! upp] & l[] surfaces w be m gr\nd at ! edges1 :ile 9 ! opposite ev5t ! c5tre w be *iefly affect$4 ,fig4 #ea4 ,a sph]omet] capable ( measur+ a #b-;in* surface may be procur$1 hav+ a screw (1 say1 #ej ?reads to ! in*1 & a micromet] surface divid$ into #bjj p>ts1 ea* "p easily capable ( subdivision--into t5?s or ev5 tw5tie?s4 ,to get ! full advantage ( ! sph]omet] x mu/ screw exce$+ly freely 7i4e4 mu/ be well oil$ ) clock oil71 & mu/ n be f+]$ except at ! mill$ head4 ,if "o ( ! legs is held by ! f+]s ! expansion is suffici5t to ?r[ ! in/rum5t q out ( adju/m5t4 ,! glass-gr9d+ tools be+ br\ght to ! prop] figure1 ! next process is to transf] ! same to ! l5s1 & ?is is done by simil> means1 ! fell[ tool be+ us$ to correct ! "o employ$ 9 gr9d+ ! l5s surface4 ,be=e ! grade ( em]y is *ang$ all ?ree surfaces mu/ agree1 z ne>ly1 at lea/1 z ! sph]omet] w %[4 ,9 ord] to prev5t confusion ! foll[+ summ>y ( ! /eps already tak5 may be giv54 ,! discs ( glass are fir/ gr\nd or turn$ s z to be truly circul>4 ,f\r tools are made = ea* surface--a r\gh pair ( iron or lead1 & a f9i%+ pair ( iron1 lead1 or slate fac$ by glass squ>es4 ,= a small l5s ! iron or lead back+ may be us$1 = a l>ge "o ! slate4 ,! r\gh tools are us$ to give an approximate figure bo? to ! l5s & to ! f9i%+ tools4 ,! f9al adju/m5t is atta9$ by gr9d+ "o ( ! glass-fac$ tools alt]nately ^u ! l5s & ^u ! fell[ glass-fac$ tool4 ,! sph]omet] is accept$ at all /ages ( ! process z ! f9al arbit] z to curvature4 ,"s h9ts on ! =m ( /rokes us$ 9 gr9d+ w be giv5 lat] on 7see #fa74 ,x suffices to /ate "h t ! object ?r\gh\t is to secure uni=mity by all[+ bo? ! "w & ! tool to rotate1 & ex]cis+ no pressure by ! f+]s4 ,! tool back+ may weigh f "o to two p\nds = a #b-;in* l5s4 #fj4 ,! tools & l5s be+ all ( ! same curvature1 ! /ate ( ! surface is gradually improv$ by gr9d+ ) f9] & f9] em]y4 ,! be/ way ( grad+ ! em]y is by wa%+ x ) clean wat]1 & all[+ ! em]y 7at fir/ /irr$ up ) ! wat]7 to settle out4 ,! long] ! "t requir$ = ?is "p ( ! process ! f9] w be ! em]y deposit$4 ,an ord9>y b$room jug is a v good ut5sil to employ dur+ ?is process2 a l>ge glass jug is ev5 bett]4 ,! foll[+ grades w be f\nd suffici5t1 ?\gh ,i d>esay e op]ative's practice diff]s a little on ?is po9t4 #a/ grade3 ,fl\r em]y1 ) ! grit wa%$ out1 i4e4 all[$ to /& = #b 7sec47 be=e be+ p\r$ (f4 #bnd grade3 ,/& #e 7secs471 settle 9 #a' 7m947 #crd grade3 ,/& #a'1 settle 9 #aj'4 #d? grade3 ,/& #aj'1 settle 9 #fj'4 ,x is g5]ally advisable to repeat ! wa%+ process ) ea* grade4 ,?us1 select+ grade #b = illu/ration1 ! liquor = grade #c mu/ be p\r$ (f )\t all[+ any ( ! s$im5t to pass ov] ) x4 ,if any s$im5t at all passes1 "o has no security aga9/ its conta9+ p]haps ! l>ge/ p>ticle 9 ! jug4 ,z soon z ! liquor = ,no4 #c has be5 decant$1 jug ,no4 #b is fill$ up aga9 ) clean wat] 7filt]$ if necess>y71 & aft] /&+ #e is decant$ into jug ,no4 #b;b1 ! s$im5t is return$ to jug ,no4 #a1 & ! liquor1 aft] /&+ #a'1 is transf]r$ to jug ,no4 #c4 ,! greate/ c>e is necess>y at ea* /ep ( ! op]ation to prev5t s$im5t pass+ ov] ) liquor4 ,!re is a little dang] f ! t5d5cy :i* ev5 comp>atively l>ge p>ticles ( em]y h to float1 9 consequ5ce ( _! refus+ to get wet1 & ! em]y work$ up on ! side ( ! jug is also a s\rce ( dang]1 !re=e wipe ! jug r\nd inside be=e decant+4 ,9 ord] to get a uni=m grade /op ! curr5ts ( wat] 9 ! jug1 :i* may "w up co>se p>ticles1 by hold+ a ?9 bit ( wood 9 ! rotat+ liquid = a mom5t1 & !n g5tly )draw+ x 9 its own plane4 ,^! precautions are p>ticul>ly necess>y 9 ! case ( grades ,nos4 #b1 #c1 & #d1 especially ,no4 #d1 = if a s+le co>se p>ticle gets on ! tool :5 ! "w has progress$ up to ?is po9t x w probably necessitate a return to gr9d+ by means ( ,no4 #b1 & involve _m h\rs' "w4 ,! surface ( ! l5s w require to be gr\nd cont9u\sly ) ea* grade till x has ! uni=m /ate ( r\ghness correspond+ to ! grade 9 "q4 ,two h\rs = ea* grade is ab\t ! usual "t requir$ 9 work+ su* a l5s z is "h contemplat$4 ,! co>s] grades ( em]y may be obta9$ by wa%+ ord9>y fl\r ( em]y1 b ! f9] ones h to be got f em]y :i* has be5 us$ 9 ! previ\s processes4 ,x is n a good plan to wa% ! f9] grades ( em]y out ( ! proce$s ( v r\gh gr9d+ say ) any?+ co>s] ?an fl\r ( em]y--z !re is a dang] ( !reby contam9at+ ! f9] grades ) comp>atively co>se glass p>ticles 7ow+ to _! lightness7 & ?is may lead to scrat*+4 ,if ! f9] grades are v light 9 col\r1 x may be inf]r$ t a consid]able portion ( ! du/ is compos$ ( glass1 & ?is does no good4 ,consequ5tly "t may be sav$ by /irr+ up ! light-col\r$ mass ) a little hydr(luoric acid 9 a plat9um capsule2 ?is dissolves ! f9ely divid$ glass almo/ in/antane\sly4 ,! em]y & excess ( hydr(luoric acid may !n be ?r[n into a l>ge beak] ( clean wat] & wa%$ sev]al times4 ,f9e em]y ?us treat$ has mu* ! same d>k *ocolate col\r z ! co>s] v>ieties4 ,! op]ator %\ld n we> a coat1 & %\ld h 8 arms b>e :ile work+ ) f9e em]y1 = a work%op coat is sure to h ga!r$ a good deal ( du/1 & increases ! *ances ( co>se p>ticles gett+ betwe5 ! surfaces4 #fa4 ,details ( ! ,process ( ,f9e ,gr9d+4 ,a l5s ( ! size select$ = description is m\nt$ z be=e m5tion$ on a lead5 p$e/al1 & ! op]ator places ! latt] on a table ( conv5i5t height 9 a room z free f du/ z possible4 ,ev]y?+ %\ld be z clean z a p91 & no spla%es ( em]y mud %\ld be all[$ to lie ab\t4 ,i h f\nd x conv5i5t to spread clean newspap]s on ! table & floor1 & to we> clean l95 clo!s1 :i* d n pick up du/4 ,i h an idea t 9 l>ge work%ops "s simpl] means ( avoid+ scrat*es mu/ h be5 discov]$1 b ,i c only give ! results ( my own exp]i5ce4 ,i nev] successfully avoid$ scrat*es till ,i adopt$ ! precautions m5tion$4 ,fig4 #eb4 ,! left h& %\ld be employ$ 9 rotat+ ! p$e/al ei!r cont9u\sly 7?\gh sl[ly7 or at int]vals (1 say1 "o m9ute4 ,?is po9t is r important4 ,"s op]ators require two h&s to "w ! gr9d+ tool1 & 9 any case ?is is ! saf] practice4 ,"u ^! circum/ances ! p$e/al may be rotat$ ?r\gh "o-eigh? or t5? ( a revolution e ?ree m9utes1 or !reab\ts4 ,! g5]al motion giv5 to ! gr9d+ tool %\ld be a s]ies ( circul> sweeps ( ab\t "o-f\r? ! diamet] ( ! glass disc1 & gradually c>ri$ r\nd an imag9>y circle drawn on ! surface ( ! l5s & conc5tric ) x 7,fig4 #eb74 ,! tool may ov]hang ! l5s by a qu>t] ( ! diamet] ( ! latt] z a maximum4 ,! circuit may be complet$ 9 f twelve to ?irty sweeps4 ,! gr9d+ tool %\ld be lightly held by ! f+]s & ! necess>y =ce appli$ p>allel to ! surface4 ,! tool itself mu/ be sl[ly rotat$ ab\t its axis ( figure4 ,if ! tool be lightly held1 x w be f\nd t x t5ds to rotate by itself4 ,i say t5ds to rotate1 = if ! tool be t\*+ ev5ly all ov] ! surface x w rotate 9 a direction opposite to ! direction ( ! circul> sweep4 ,= in/ance1 if ! tool be c>ri$ r\nd its loop$ pa? clockwise1 x w t5d to rotate ab\t its own axis ( figure c\nt]-clockwise4 ,if x t\* m 9 ! middle1 ?is rotation w be increas$1 :ile if x t\*es m along ! edge1 ! rotation w be dim9i%$1 or ev5 rev]s$ 9 an extreme case4 ,e fifty sweeps or s ! tool %\ld be simply gr\nd backw>ds & =w>ds along a diamet] ( ! l5s surface4 ,?is gr9d+ %\ld consi/ ( ?ree or f\r j\rneys to & fro along1 say1 eight diff]5t diamet]s4 ,ab\t "o-qu>t] ( ! :ole gr9d+ %\ld be accompli%$ by %ort /raight /rokes1 dur+ :i* ! tool %\ld only ov]hang ab\t "o-qu>t] ( an in*4 ,! object ( ! /raight /rokes is to c\nt]act ! t5d5cy to a gradual accumulation ( ! em]y 9 ! c5tre1 :i* results f ! circul> gr9d+4 ,a great deal ( ! art ( ! process consi/s 9 kn[+ h[ to "w ! tool to produce any giv5 effect4 ,= in/ance1 if ! l5s requires to be gr\nd d[n ne> ! c5tre1 ! epicycloidal /rokes mu/ be ne>ly c5tral2 ! tool mu/ nev] ov]hang v mu*4 ,if1 on ! o!r h&1 x is ! edges :i* require att5tion1 ^! mu/ be dealt ) by wid] ov]hang+ /rokes4 ,! tool mu/ be frequ5tly te/$ on its fell[1 &1 inde$1 gr\nd ^u x if any m>k$ unev5ness ( action 7su* z t j describ$7 is requir$ = ! l5s4 ,a *eck by sph]omet] w be appli$ at int]vals accord+ to ! judgm5t ( ! op]ator1 b1 9 any case1 ! fell[ tool & l5s %\ld be kept at v ne>ly ! same figure4 ,! em]y %\ld nev] be all[$ to become any?+ l dry betwe5 ! tool & ! l5s1 = 9 "s way 7probably by capill>y action increas+ ! pressure ( ! tool7 ?is seems to lead to scrat*+ & roll+ ( ! em]y4 ,! *annels 9 ! glass tool betwe5 ! squ>es are ( ! greate/ importance 9 enabl+ ! em]y to di/ribute itself4 ,p]haps ! be/ guide 9 enabl+ "o to judge z to :5 x is "t to wa% (f ! em]y & apply fre% is ! feel ( ! tool2 also :5 ! mud gets light 9 col\r we "k t x is full ( glass du/1 & proportionately inop]ative4 ,new em]y may be put on1 say1 e five m9utes1 b no absolute rule c be giv51 = mu* dep5ds on ! pressure ( ! tool ^u ! l5s4 ,9 ! case consid]$ a brass or lead1 or ev5 slate tool1 ( an in*1 or ev5 less1 9 ?ickness1 w press q heavily en\gh4 ,9 wa%+ ! l5s & tool be=e new em]y is introduc$1 a l>ge enamell$ iron bucket is v h&y2 ! :ole ( ! tool %\ld be imm]s$ & scrubb$ ) a nail-bru%4 ,! l5s surface may be wip$ ) a bit ( clean sponge1 free f grit1 or ev5 a clean damp clo?4 ,:5 ! "t comes to alt] ! grade ( em]y1 a fre% lot ( newspap]s %\ld be put d[n1 & tools1 l5s1 & p$e/al well wa%$ & bru%$ by ! nail-bru%4 ,! surfaces %\ld be wip$ dry by a fre% piece ( rag1 & exam9$ = scrat*es & also = uni=mity ( appe>ance2 a good op9ion c be =m$ z to ! fit ( ! surfaces by not+ :e!r--& if s1 to :at degree--!y diff] 9 appe>ance f po9t to po9t :5 held s t ! light falls on !m obliquely4 ,x is necess>y to ex]cise ! greate/ c>e 9 ! wa%+ betwe5 ! application ( successive grades ( em]y1 & ?is w be facilitat$ if ! edges ( ! glass squ>es 7 dress$ on a gr9d/one be=e !y 7 m\nt$4 ,an additional precaution :i* may be ( imm5se advantage is to all[ ! tool to dry betwe5 ! application ( successive grades ( em]y 7( c\rse1 aft] x has be5 scrubb$71 & !n to bru% x vigor\sly ) a hat-bru%4 ,x sometimes happ5s t p>ticles ( mud :i* h resi/$ ! wet scrubb+ ) ! nail-bru% may be remov$ by ?is me?od4 ,z my fri5d ,mr4 ,cook in=ms me t 8 pres5t practice diff]s slightly f ! above1 ,i w dep>t f ! rule ,i laid d[n1 & add a note on an alt]native me?od4 ,consid] a s+le l5s surface4 ,?is is r\gh$ out z be=e by an iron tool1 a r\gh fell[ tool be+ made at ! same "t4 ,! squ>es ( glass are cem5t$ to ! r\gh+ tool1 & ?is is gr\nd to ! sph]omet] by means ( ! c\nt]p>t tool4 ,! glass-coat$ tool is !n appli$ to ! l5s surface & gr9d+ ) ! fir/ grade ( em]y comm5c$4 ,! curvature is *eck$ by ! sph]omet]4 ,two auxili>y tools (1 say1 half ! diamet] ( ! l5s1 are prep>$ f slate1 or glass back$ ) iron1 & appli$ to gr9d d[n ei!r ! c5tral "p ( ! l5s surface or tool surface1 accord+ to ! indications ( ! sph]omet]4 ,any *anges t may occur dur+ gr9d+ are correct$ by ^! tools4 ,! sph]omet] is accept$ z ! sole guide 9 obta9+ ! prop] curvature4 ,a slate back+ is pref]r$ = tools ( any diamet] ov]1 say1 #b in*es4 #fb4 ,poli%+4 ,aft] ! surface has be5 gr\nd ) ! la/ grade ( em]y1 & comm5ces to become transluc5t ev5 :5 dry1 ! gr9d+ may be consid]$ to be accompli%$1 & ! next /ep is ! poli%+4 ,!re are _m ways ( c>ry+ out ?is process1 & ! relative suitability ( ^! me?ods dep5ds on a good _m1 s to speak1 accid5tal circum/ances4 ,= in/ance1 if ! int5tion is to f9i% ! poli%+ at a sitt+1 ! poli%+ tool may be fac$ ) squ>es ( ar*angel--n m9]al or coal-t>--pit* & br\ght to %ape simply by press+ :ile w>m aga9/ ! face ( ! l5s4 ,a tool ?us made is v conv5i5t1 accurate1 & good1 b x is difficult to keep x 9 %ape = any l5g? ( "t2 if left on ! l5s x is apt to /ick1 & if x ov]hangs ev] s little w1 ( c\rse1 droop at ! edges4 ,on ! :ole1 ! foll[+ w be f\nd a good & suffici5t plan4 ,! glass-gr9d+ tool is conv]t$ into a poli%+ tool by pa/+ a bit ( ?9 pap] ov] its surface2 a bit ( wov5 lett] pap] ( m$ium ?ickness ) a smoo? b n glaz$ surface does v well4 ,we h f\nd t :at is call$ ,smi?'s #ba lbs4 ,vellum ,wove is excell5t4 ,?is is /eep$ 9 wat] till q pliable & almo/ free f size4 ,! glass tool is bru%$ ov] ) a little ?9 arr[root or />* pa/e1 & ! pap] is laid ^u x & squeez$ d[n on ! glass squ>es z well z possible2 if ! pap] is wet en\gh & ( ! prop] quality x w exp& suffici5tly to envelop ! tool )\t creases1 unless ! curvature is q out ( ! common4 ,?is be+ accompli%$1 & ! excess ( wat] & pa/e remov$1 ! face ( ! pap] is 7= security7 wa%$ ) a little clean wat] & a bit ( sponge1 &1 f9ally1 ! tool is slightly press$ on ! l5s s z to get ! pap] to take up ! prop] figure z ne>ly z possible4 ,aft] ! poli%+ tool has be5 ?us br\ght to ! prop] figure1 x is lift$ (f & all[$ to dry sl[ly4 ,:5 ! pap] is dry x may be trimm$ r\nd ! edges s z n to project s5sibly beyond ! glass squ>es4 ,! next /ep is to bru% ! surface ov] v c>efully ) poli%+ r\ge 7prep>$ z is describ$ at ! end ( ?is section7 by means ( a hat-bru%4 ,:5 ! surface ( ! pap] is fill$ ) r\ge all excess mu/ be remov$ by vigor\s bru%+4 ,fig4 #ec4 ,! tool be+ plac$ on ! l5s1 two or ?ree /rokes simil> to ^? us$ 9 gr9d+ may be tak51 & ! tool is !n lift$ (f & exam9$4 ,x w be f\nd to be dott$ ) a few bright po9ts1 produc$ by ! adhesion ( glass at ! places ( contact4 ,^! po9ts are !n to be remov$ 9 ! foll[+ mann]4 ,an old ?ree-corn]$ file is gr\nd on ea* side till ! file m>ks disappe>1 & %>p edges are produc$ 7,fig4 #ec74 ,?is tool is us$ z an ink eras]1 & x w be f\nd to scrape ! pap] ( ! poli%+ tool v cleanly & well4 ,! bright spots are ! objects ( att5tion1 & !y mu/ be eras$ by ! old file1 & ! poli%] reappli$ to ! glass4 ,a few /rokes w develop o!r po9ts1 m num]\s ?an be=e1 & ^! 9 turn mu/ be eras$4 ,! process is cont9u$ till ! :ole surface ( ! poli%+ tool is ev5ly cov]$ ) bright specks1 & !n ! poli%+ may be proce$$ )4 ,! specks %\ld n be m ?an ab\t "o-eigh? ( an in* ap>t1 or ! poli%+ w be irregul>4 ,! op]ation ( poli%+ is simil> to t ( gr9d+4 ,a reasonable "t = poli%+ a glass surface is tw5ty h\rs2 if m "t is requir$ x is a sign t ! f9e gr9d+ has n be5 c>ri$ f> en\gh4 ,! progress ( ! op]ation may be be/ wat*$ by look+ at ! surface--n ?r\gh x4 ,= ?is purpose a good light is requisite4 ,:5 ! l5s is dism\nt$ x may be exam9$ by a beam ( sunlight 9 a d>k room1 "u :i* circum/ances ! fa9te/ signs ( grayness are easily disc]nible4 ,x may be m5tion$ "h t if ! surface is 9 any way scrat*$ ! r\ge w lodge 9 ! scrat*es ) great p]si/5ce1 & an exp]t c g5]ally tell f ! appe>ance ( scrat*es :at k9d ( poli%+ p[d] has be5 employ$4 ,! p]si/5ce ) :i* r\ge cl+s to a r\gh surface ( glass is r rem>kable4 ,"s glass poli%]s pref] to use putty p[d] z a poli%+ mat]ial1 & x is sometimes said to act m quickly ?an r\ge2 f my r limit$ exp]i5ce ,i h n f\nd ?is to be ! case1 b x may h m]its t ,i d n "k (4 ,is x possible t its recomm5dation lies 9 ! fact t x does n r5d] scrat*es s obtrusively obvi\s z r\ge does8 ,r\ge is g5]ally made 9 two or m grades4 ,! s(t] grade is us$ = poli%+ silv]1 & is call$ jewell]s' r\ge4 ,! h>d] grade1 suitable = glass poli%+1 is be/ obta9$ f practical opticians 7n m]e sell]s ( optical in/rum5ts74 ,i mean p l ,messrs4 ,cook ( ,york4 ,_m ye>s ago ,i prep>$ my own h>d r\ge by precipitat+ f]r\s sulphate solution by aque\s ammonia1 wa%+ ! precipitate1 & heat+ x to a r$ heat4 ,! product 0 gr\nd up ) wat]1 & wa%$ to get rid ( l>ge p>ticles4 ,?is answ]$ e purpose1 & ,i c\ld n f9d t x 0 9 any way inf]ior to h>d r\ge z pur*as$4 ,! same precipitate heat$ to a l[] temp]ature is said to furni% a s(t] v>iety ( r\ge2 at all ev5ts1 x gives "o m suitable = poli%+ speculum metal4 ,"l ,rosso us$ r\ge heat$ to a dull r$ness = ?is purpose4 ,r\ge1 :e!r made or b\ght1 %\ld always be wa%$ to get rid ( grit4 ,i ought to add t n ! lea/ rem>kable fact ab\t ! poli%+ is ! extraord9>ily small quantity ( ! poli%+ mat]ial requisite1 :i* sugge/s t ! process ( poli%+ is n by any means ! same z t ( exceptionally f9e gr9d+4 ,is x possible t ! *ief proximate cause ( ! utility ( r\ge is to be s\ght 9 its curi\s prop]ty ( adh]+ to a r\gh glass surface1 caus+ x1 s to speak1 to drag ! glass (f 9 m9ute quantities1 & r$eposit x aft] a c]ta9 ?ickness has be5 atta9$ on ano!r "p ( ! surface8 #fc4 ,c5t]+4 ,:5 a l5s is gr\nd & poli%$ x w almo/ always happ5 t ! axis ( revolution ( its cyl9drical edge is incl9$ to ! axis ( revolution ( its curv$ surfaces4 ,s9ce 9 practice l5ses h to be adju/$ by _! edges1 x is g5]ally necess>y to adju/ ! edge to a cyl9d] ab\t ! axis ( figure ( ! active surfaces4 ,?is is be/ done on a la! ) a holl[ m&rel44 ,! l5s is *uck$ on a *uck ) a c5tral ap]ture--g5]ally by means ( pit* or ,regnault's ma/ic1 or c5t]+ cem5t = small l5ses--& a cross wire is fix$ 9 ! axis ( revolution ( ! la!1 & is illum9at$ by a lamp4 ,?is cross wire is obs]v$ by an eye-piece 7) cross wires only 9 ! case ( a convex l5s1 or a telescope simil>ly furni%$ 9 ! case ( a concave l5s71 also plac$ 9 ! axis ( rotation ( ! la!4 ,bo? cross wires are ?us 9 ! axis ( revolution ( ! m&rel1 & ! di/ant "o 7,b 9 ! figure7 is view$ ?r\gh ! l5s & ref]r$ to ! fix$ cross wires at ,a4 ,9 g5]al1 z ! la! is rotat$ by turn+ ! m&rel ! image ( ! illum9at$ cross wires w be obs]v$ to rotate also4 ,! l5s is adju/$ until ! image rema9s /eady on rotat+ ! m&rel & x is to give "t = ?is op]ation t a sl[-sett+ cem5t is recomm5d$4 ,:5 ! image rema9s /ation>y we "k t ! optical c5tre ( ! l5s is 9 ! axis ( revolution1 & t ?is axis is normal to bo? l5s surfaces1 i4e4 is ! pr9cipal axis ( ! l5s1 or axis ( figure4 ,fig4 #ed4 ,a mu* readi] me?od1 & "o1 9 g5]al1 good en\gh = mo/ purposes1 is to put a c&le on ! end ( ! la!-b$ :]e ! back c5tre g5]ally is1 & obs]ve ! images ( ! flame by reflection f bo? ! l5s surfaces4 ,?is me?od is v h&y ) small l5ses2 ! m&rel is turn$1 & ! l5s adju/$ by h& till ! images are immovable4 ,9 bo? cases1 ( c\rse1 ! edge ( ! l5s is turn$ or gr\nd till x is truly circul>1 ! position ( ! l5s rema9+ undi/urb$ on ! *uck4 ,if ! edge gauge has be5 prop]ly us$ 9 ! e>li] /ages ( figur+1 x w be f\nd t v little turn+ or gr9d+ is requisite to produce a true c5t]+4 ,! p>ticul> defect due to want ( c5t]+ 9 a l5s may be obs]v$ by us+ x z ! objective ( a telescope1 & obs]v+ a /> slightly out ( focus4 ,! int]f]5ce fr+es w n be conc5tric circles unless ! l5s is prop]ly c5tr$4 ,i ought to say t ,i h n look$ into ! !ory ( ?is1 b h m]ely tak5 x z a g5]ally admitt$ fact4 ,! diseases ( l5ses & ! modes ( treat+ !m are dealt ) 9 a book by ,messrs4 ,cook ( ,york1 entitl$ ,on ! ,adju/m5t & ,te/+ ( ,telescopic ,objectives4 ,! f9al process ( figur+ w be dealt ) lat] on 7 #ff & #fg71 z x applies n only to l5ses b to mirrors1 prisms1 etc4 ,if ! in/ructions giv5 h be5 c>efully c>ri$ out on a #b-;in* l5s1 x %\ld p]=m fairly well1 & possibly p]fectly1 )\t any fur!r adju/m5t ( ! glass4 #fd4 ,prep>ation ( ,small ,l5ses1 :]e great ,accuracy is n ( ! fir/ ,importance4 ,su* l5ses may g5]ally be made out ( bits ( good plate or %eet glass1 & are ( con/ant use 9 ! physical laboratory4 ,!y may be pur*as$ s *eaply1 h[ev]1 t only ^? :o h ! mis=tune to "w 9 out-(-!-way places ne$ be driv5 to make !m4 ,suitable glass hav+ be5 obta9$ & ! curves calculat$ f ! index ( refraction1 z obta9$ by any ( ! ord9>y me?ods applicable to plates 7! microscope me?od1 9 g5]al1 is q good en\gh71 squ>es circumscrib+ ! desir$ circles are cut out by ! help ( a diamond4 ,footnote3 ,glazebrook & ,%aw's ,practical ,physics1 p4 #chc 7#d? ed474 ,! squ>es are r\ghly snipp$ by means ( a pair ( pli]s or spectacle-mak]'s %anks4 ,! r\gh circles are !n m\nt$ on ! end ( a brass or iron rod ( r great] diamet] ?an ! f9i%$ l5ses are to possess4 ,?is m\nt+ is be/ done by c5t]+ cem5t4 ,! discs are !n dress$ circul> on a gr9d/one1 ! rod s]v+ bo? z a gauge & h&le4 ,a suffici5t numb] ( ^! discs hav+ be5 prep>$1 a pair ( brass tools ( ! =m %[n 9 ! sket* 7,fig4 #ee71 & ( ab\t ! prop] radius ( curvature1 are made4 ,"o ( ^! tools is us$ z a support = ! glass discs4 ,fig4 #ee4 ,a compass be+ set to scribe circles ( ! same diamet] z ! glass discs1 c5tre m>ks are made on ! surface ( ! appropriate tool1 circles are drawn on ?is1 & facets are fil$ or mill$ 7= :i* ! spiral head ( ! mill+ ma*9e is excell5t74 ,9 ! case ( concave support+ surfaces1 i4e4 9 mak+ concave l5ses1 ,i appreh5d fil+ w\ld be difficult1 & ! facets w\ld h to be made by a rose cutt] or mill2 b if ! discs are fairly r\nd1 !n1 9 fact1 no facets are requir$4 ,! facets be+ ready1 ! glass discs are cem5t$ to !m by c5t]+ cem5t1 :i* may be us$ q g5]ally = small l5ses4 ,:5 ! cutt+ ( facets has be5 omitt$ on a concave surface1 ! be/ cem5t is h>d pit*4 ,! gr9d+ tool is g5]ally r l>g] ?an ! ne/ ( l5ses4 ,co>se & f9e gr9d+ is accompli%$ :olly on ! la!--! tool be+ rotat$ at a fair spe$ 7see infra71 & ! ne/ ( l5ses mov$ ab\t by its h&le s z to gr9d all p>ts equally4 ,x mu/1 ( c\rse1 be held any:]e except dead on1 = !n ! "p r\nd ! axis w\ld n get gr\nd2 ?is inop]ative portion ( ! rotat+ tool mu/ !re=e be all[$ to di/ribute its incapable ef=ts ev5ly ov] ! ne/ ( l5ses4 ,poli%+ is accompli%$ by means ( ! gr9d+ tool1 coat$ ) pap] & r\ge z be=e2 or ! tool may be coat$ ) v ?9 clo? & us$ ) r\ge z be=e--9 ?is case ! poli%+ goes on fa/e/ :5 ! surface ( ! clo? is di/9ctly damp4 ,9 work+ by ?is me?od1 ea* grade ( em]y ne$ only be appli$ f five to t5 m9utes4 ,! glass does n appe> to get scrat*$ :5 ! em]y is *ang$1 provid$ ev]y?+ is well wa%$4 ,a good poli% may be got 9 an h\r4 ,! la! is run z = turn+ brass ( ! same diamet] z ! tool4 ,"o side ( ! l5ses be+ ?us prep>$1 !y are rev]s$1 & ! process gone ?r\gh = ! o!r side 9 a precisely simil> mann]4 ,footnote3 ,unless ! radius ( curvature is v %ort & ! l5ses also convex1 !re is no necessity to recess ! facets1 provid$ h>d pit* is us$ z ! cem5t4 ,see note on h>d pit*4 ,to save tr\ble1 x is usual1 to make su* l5ses ( equal curvature on bo? faces2 b ( c\rse ?is is a matt] ( ta/e4 ,fig4 #ef4 ,= v common "w1 bits ( good plate glass are employ$1 & ! manufactur]'s surface treat$ z flat 7,fig4 #ef74 ,9 ?is way plano-convex l5ses are easily & *eaply made4 ,f9ally ! l5ses h to be c5tr$1 an ess5tial op]ation 9 ?is case4 ,?is is easily done by ! reflection me?od--! edge be+ turn$ (f by ! file & k]os5e & ! c5t]+ cem5t be+ us$ 9 mak+ ! prelim9>y adju/m5t on ! *uck4 ,i presume a l5s made 9 ?is way is wor? ab\t a %ill+1 s t laboratory manufacture is n v remun]ative4 ,fig4 #ef %[s ! me?od ( m\nt+ small l5ses = la! gr9d+1 :5 only "o l5s is requir$4 ,! tool is g5]ally rotat$ 9 ! la! & ! l5s held aga9/ x4 #fe4 ,prep>+ ,small ,mirrors = ,galvanomet]s4 ,to get good mirrors = galvanomet]s1 ,i h f\nd ! be/ plan is to gr9d & poli% a l>ge numb] toge!r1 on a disc p]haps #h or #aj in*es 9 diamet]4 ,i 0 l$ to ?is aft] inspect+ & reject+ f\r ounces ( microscope cov] slips1 a mo/ we>isome process4 ,t regul> cov] slips %\ld be few & f> betwe5 is n unlikely1 see+ t !y are made 7by "o em95t firm at lea/7 simply by pot bl[+ a huge ?9 bulb1 & !n sma%+ x on ! floor & select+ ! fragm5ts4 ,z 9 ! case ( l>ge mirrors1 x is ( c\rse only necess>y to gr9d "o side ( ! glass1 !oretically at all ev5ts4 ,! objections to ?is c\rse are3 7#a7 ,a silv] surface _c1 9 my exp]i5ce1 be poli%$ ext]nally 7on a m9ute object l a cov] slip7 to be any?+ l s bright z ! silv] surface next ! glass2 &1 7#b7 if "o side only is gr\nd1 x w be f\nd t ! little mirror hopelessly loses its figure directly x is deta*$ f ! support on :i* x has be5 work$4 ,consequ5tly1 ,i recomm5d t ^! small mirrors %\ld be gr\nd & poli%$ on bo? sides--en\gh may be made at "o op]ation to la/ = a v long "t4 ,a slate back is prep>$ ( ! same radius ( curvature z x is desir$ to imp>t to ! mirrors4 ,bits ( ?9 %eet glass are !n gr\nd circul> z describ$ 9 ! la/ section & cem5t$ to ?is surface by ! smalle/ quantity ( clean ar*angel pit*1 all[$ to cool sl[ly & ev5 to re/ = a day be=e ! "w is proce$$ )4 ,! :ole surface is !n gr\nd & poli%$ z be=e4 ,! mirrors are n[ rev]s$1 :5 !y ought to ne>ly fit ! tool 7assum+ t flats are be+ made1 & ! fell[ tool 9 all o!r cases71 & are recem5t$ by pit* to ! appropriate back+ gr\nd1 & poli%$4 ,if v excell5t results are requir$1 ^! processes may be prec$$ by a prelim9>y r\gh gr9d+ ( "o surface1 s t ! little discs w sit exactly on ! tool surface1 & n run ! risk ( be+ /ra9$ by capill>y =ces 9 ! pit*4 ,we h always f\nd ?is necess>y = really good results4 ,on remov+ su* mirrors f ! back+1 !y g5]ally1 m or less lose _! figure1 becom+ 79 g5]al fairly uni=mly7 m concave or convex4 ,ab\t #e p] c5t ( ! mirrors ?us prep>$ w be f\nd almo/ p]fect if ! "w has be5 well done1 & ! re/ w probably be v fair1 unless ! diamet] is v l>ge z comp>$ ) ! ?ickness4 ,! be/ way ( gr9d+ & poli%+ su* l>ge surfaces 7ne/s #aj in*es 9 diamet]7 is on a gr9d+ ma*9e1 su* z w be describ$ bel[4 ,! poli%+ is be/ done by means ( pap]1 z be=e describ$4 ,hav+ occasion to require hi!rto unapproa*$ lightness & optical accuracy 9 su* mirrors1 ,i got my assi/ant to try mak+ !m ( fus$ qu>tz1 slices be+ cut by a diamond :eel f a rod ( t mat]ial4 ,*ips ( natural qu>tz 7 also obta9$ f brok5 pebble spectacles1 & ^! 7 work$ at ! same "t4 ,! result+ mirrors 7 c]ta9ly sup]ior to ! be/ we c\ld make f glass1 b ! lab\r ( gr9d+ 0 great]1 & ! lab\r ( poli%+ less1 ?an 9 ! latt] case4 ,! pebble fragm5ts gave practically z good mirrors z ! fus$ slices4 ,= ! future x w be bett] always to make galvanomet] mirrors f qu>tz cry/als4 ,^! may be easily slic$1 z w be describ$ 9 #gd4 ,! slices are dress$ on a gr9d/one accord+ to in/ructions already giv5 = small l5ses4 ,! silv]+ ( ^! mirrors is a po9t ( great importance4 ,aft] try+ ne>ly e =mula publi%$1 we h settl$ d[n to ! foll[+4 ,a solution ( pure cry/allis$ nitrate ( silv] 9 di/ill$ wat] is made up to a /r5g? ( #abe grams ( ! salt p] litre4 ,?is =ms ! /ock solution & is kept 9 a d>k bottle4 ,let ! volume ( silv]+ liquor requir$ 9 any op]ation be d5ot$ by #d v4 ,! liquor is prep>$ z foll[s3 ,i4 ,measure out a volume v ( ! /ock solution ( silv] nitrate1 & calculate ! weight ( salt :i* x conta9s2 let ?is be w4 ,9 ano!r vessel dissolve pure ,ro*elle salt to ! am\nt ( #b4f w1 & make up ! solution to ! volume v4 ,^! two solutions are to be mix$ toge!r at a temp]ature ( #ee ,c1 ! vessels ) _! cont5ts be+ heat$ to ?is temp]ature on ! wat] ba?4 ,aft] mix+ ! liquids ! temp]ature is to be kept approximately con/ant = five m9utes1 aft] :i* ! liquor may be cool$4 ,! :ite precipitate :i* fir/ =ms w become gray or black & v d5se z ! liquid cools4 ,if x does n1 ! liquor mu/ be reheat$ to #ee ,c1 & kept at t temp]ature = a few m9utes & !n aga9 all[$ to cool4 ,! solution is 9 good ord] :5 all ! precipitate is d5se & gray or black & ! liquor cle>4 ,! black] & d5s] ! precipitate ! bett] is ! solution4 ,! liquor is decant$ & filt]$ f ! precipitate & br\ght up to ! volume #b v by addition ( "s ( ! wa% wat]4 ,,ii4 ,measure out a volume #j4aah v ( ! /ock solution into a sep>ate vessel1 & add to x a #e p] c5t solution ( ammonium hydrate1 ) prop] precautions1 s t ! precipitate at fir/ =m$ is all b r$issolv$ aft] vigor\s %ak+4 ,x is v important t ?is condition %\ld be exactly atta9$4 ,!re=e add ! latt] "p ( ! ammonia v c>efully4 ,make up ! volume to #b v4 ,mix ! solutions ,i4 & ,,ii4 9 a sep>ate vessel & p\r ! mixture into ! deposit+ vessel4 ,! surface to be silv]$ %\ld face d[nw>ds1 & lie j b5ea? ! free surface ( ! liquid4 ,bubbles mu/ ( c\rse be remov$4 ,! silv] deposit obta9$ 9 ?is mann] is exce$+ly :ite &1 bright on ! surface next to ! glass1 b ! back is mat & requires poli%+4 ,! detail ( ! process describ$ above 0 work$ out 9 my laboratory by ,mr4 ,a4 ,pollock1 to :om my ?anks are due4 ,?is process gives good deposits :5 ! solutions are fre%ly prep>$1 b ! ammonia solution w n keep2 ,! surfaces to be silv]$ require to be absolutely clean4 ,! process is assi/$ by a summ] temp]ature1 say #gj ,fahr1 & possibly by ! action ( light4 ,six or sev5 h\rs at lea/ are requir$ = a good deposit2 a good plan is to leave ! mirrors 9 ! ba? all night4 ,on removal f ! ba? ! mirrors require to be well wa%$1 & all[$ to dry ?or\ghly 9 sun heat = sev]al h\rs be=e !y are t\*$4 ,c>e %\ld be tak5 n to pull ! mirrors out ( %ape :5 !y are m\nt$ = ! ba?4 ,a s+le drop ( v>ni% or pa9t 7a m]e speck7 on ! c5tre w suffice to hold !m4 ,! back ( ! deposit requires to be v>ni%$ or pa9t$ z a rule to pres]ve ! silv]4 ,all pa9ts & v>ni%es ?us appli$ t5d to spoil ! figure by exp&+ or contract+4 ,on ! :ole1 ,i ?9k boil$ l9se$ oil & :ite or r$ lead--:ite or r$ pa9t 9 fact--is less delet]i\s ?an o!r ?+s ,i h tri$4 ,%ellac v>ni% is ! wor/4 ,( c\rse1 ! be/ mirror c be easily spoil$ by bad m\nt+4 ,i h tri$ a great numb] ( me?ods & c recomm5d z fairly successful ! foll[+3- ,a little pure :ite lead1 i4e4 b\ght z pure z a *emical--n z a pa9t--is mix$ ) an equal quantity ( r$ lead & made into a pa/e ) a little l9se$ oil4 ,i say a pa/e1 n putty4 ,a trace ( ?is is !n work$ on to ! back ( ! mirror at ! c5tre z ne>ly z may be1 & to ?is is atta*$ ! support4 ,! only objection to ?is is t ne>ly a week is requir$ = ! pa/e to set4 ,if p mu/ use %ellac let x be rememb]$ t x w g on *ang+ its %ape = mon?s aft] x has cool$ 7:e!r x has be5 dissolv$ 9 alcohol or n74 #ff4 ,prep>ation ( ,l>ge ,mirrors or ,l5ses = ,telescopes4 ,s mu* has be5 writt5 on ?is subject by a/ronom]s1 g5]ally 9 ! ,engli% ,me*anic & 9 ! ,philosophical ,transactions = #ahdj1 t x might be ?\ght no?+ c\ld be add$4 ,i w only say "h t ! processes already describ$ apply p]fectly to ?is case2 b ( c\rse ,i only ref] to silv] on glass mirrors4 ,= any size ov] #f in*es 9 diamet]1 ! process ( gr9d+ & poli%+ by h&1 p>ticul>ly ! latt]1 w probably be f\nd to involve too mu* lab\r1 & a ma*9e w be requir$4 ,a description ( a modification ( ,mr4 ,nasmy?'s ma*9e--z made by my assi/ant1 ,mr4 ,cook--w be f\nd bel[4 ,!re is no difficulty 9 con/ruct+ or work+ su* a ma*9e1 & consid]$ z an all r\nd appliance1 x possesses solid advantages ov] ! simple d\ble pulley & crank arrangem5t1 :i*1 h[ev]1 f its simplicity des]ves a note4 ,two pulleys1 ,a & ,b1 ( ab\t #ah in*es diamet] by #d in*es on ! face1 are arrang$ to rotate ab\t v]tical axes1 & belt$ toge!r4 ,! %aft ( "o ( ^! pulleys is driv5 by a belt 9 any conv5i5t mann]4 ,ea* pulley is provid$ on its upp] surface ) a crank ( adju/able l5g? c>ry+ a v]tical crank-p94 ,ea* crank-p9 passes ?r\gh a #c,x #b wood5 rod1 say #c' #f long1 & ^! rods are p9n$ toge!r at _! f>!r extremities1 & ?is p9 c>ries ! gr9d+ or poli%+ tool1 or r engages loosely ) ! back ( ?is tool :i* lies bel[ ! rod4 ,x is cle> t if ! pulleys are ( comm5surable diamet]s1 & are rigidly connect$--say by belt+ :i* nei!r /ret*es nor slips--! poli%+ tool w describe a clos$ curve4 ,if1 h[ev]1 ! belt is arrang$ to slip slightly1 or if ! pulleys are ( incomm5surable diamet]s1 ! curve trac$ out by ! gr9d+ tool w be v complex1 & 9 ! case ( ! ratio ( ! diamet]s be+ incomm5surable1 w always rema9 op52 = poli%+ purposes ! consummation to be wi%$4 ,mirror surfaces are gr\nd sph]ical1 ! r$uction to p>abolic =m be+ atta9$ 9 ! process ( poli%+4 ,a v int]e/+ acc\nt ( ! practice ( deal+ ) v l>ge l5ses w be f\nd 9 ,nature1 ,may #ahhf1 or ! ,j\rnal ( ! ,society ( ,arts1 same date 7,i presume71 by ,sir ,h[>d ,grubb4 ,! au?or consid]s t ! f9al adju/m5t ( surfaces by figur+--( :i* m anon--is an art :i* _c be le>n$ by inspection1 any m ?an a man c\ld le>n to pa9t by wat*+ an arti/4 ,?is is1 no d\bt1 ! case to "s ext5t2 /ill1 a p]son wi%+ to le>n h[ to figure a l5s c\ld n d bett] ?an take ,sir ,h[>d at 8 ^w1 & sp5d a mon? at 8 works4 ,mean:ile ! foll[+ rem>ks mu/ suffice2 x is n likely t anybody to :om ^! notes w be ( s]vice w\ld emb>k on su* l>ge "w z is contemplat$ by ,sir ,h[>d ,grubb4 ,fig4 #eg4 ,description ( ,poli%+ ,ma*9e4 ,p[] is appli$ ?r\gh belt+ to ! spe$ cone ,a4 ,by means ( a bevel p9ion rotation is communicat$ to ! :eel ,d1 :i* is ( solid metal & c>ries a ,t-slot1 ,c4 ,a p$e/al =m+ a crank-p9 c be clamp$ s z to h any desir$ radius ( motion by ! screw ,e4 ,a tra9 ( :eels ,e ,f ,g ,h ,k 7ord9>y ca/ la! *ange :eels7 communicate any desir$ ratio ( motion to ! tool-hold]1 :i* simply consi/s ( two p9s project+ v]tically d[nw>ds f ! spokes ( :eel ,k4 ,^! p9s =m a =k1 & ea* prong engages 9 a correspond+ hole 9 ! back ( ! slate-gr9d+ tool 7n %[n 9 figure74 ,! connection ) ! tool is purposely loose4 ,! :eel ,e1 ( c\rse1 _c rotate ab\t ! crank-p9 ,d4 ,provision = *ang+ ! ratio ( tool rotation is a*iev$ by m\nt+ ! :eels compos+ ! tra9 on p9s capable ( slid+ along a long slot 9 ! b> support+ !m4 ,! f>!r end ( ?is b> is caus$ to oscillate to & fro v sl[ly by means ( an additional crank-p9 ,s & crank-%aft1 ! project+ face ( ! b$-plate ,w be+ plac$ s z to all[ ,v to slide ab\t easily & smoo?ly4 ,motion is communicat$ to ?is "p ( ! sy/em by means ( ge>s at #j & ,p1 & a belt work+ f ,p to ,q4 ,?us ! v]tical %aft ,r is set 9 motion & communicates by ge>s ) ,s4 ,a pulley plac$ on ! axle ( ! :eel c>ry+ ! crank-p9 ,s gives a sl[ rotation to ! "w :i* is m\nt$ on ! table ,m4 ,a small b important feature is ! tray ,l bel[ ! ge> ,k4 ,?is prev5ts dirt fall+ f ! tee? ( ! :eel on to ! "w4 ,! motion ( ,s is ( c\rse v mu* less ?an ( ,b--say #ajj times less4 ,! "w c be conv5i5tly adju/$ z to height by means ( ! screw ,n4 ,! ma*9e mu/ be on a /eady f\ndation1 & 9 a place z free f du/ z possible4 ,?\gh x looks complicat$ x is q /raight-=w>d to build & to op]ate4 ,x is expla9$ 9 ,"l ,rayleigh's article on ,optics 9 ! ,encyclopa$ia ,britannica t a v m9ute *ange 9 ! =m ( ! curvature ( ! surface ( a l5s w make a l>ge diff]5ce 9 ! sph]ical ab]ration4 ,?is is to be expect$1 see+ t sph]ical ab]ration is a ph5om5on ( a diff]5tial sort1 i4e4 a measure ( ! diff]5ce betwe5 ! curvature actually atta9$1 & ! !oretical curvature at ea* po9t ( ! l5s1 = giv5 positions ( po9t & image4 ,sir ,h4 ,grubb gives an illu/ration ( ! m9ut5ess ( ! abrasion requir$ 9 pass+ f a curve ( "o sort to a curve ( ano!r1 say f a sph]ical to a p>abolic curve1 consequ5tly ! process ( figur+ by ! sl[ action ( a poli%+ tool becomes q intelligible4 ,9 mak+ a l>ge mirror or l5s all ! processes hi!rto describ$ "u gr9d+ & poli%+1 etc1 h to be gone ?r\gh & 9 ! mann] describ$1 & :5 all ?is is accompli%$ ! f9al process ( correct+ to te/ comm5ces4 ,?is process is call$ figur+4 #fg4 ,( ! actual op]ation ( ?is process ,i h no p]sonal k1 & ! foll[+ brief notes are drawn f ! article by ,sir ,h4 ,grubb1 f my assi/ant's 7,mr4 ,cook7 exp]i5ce1 & f a small "w ,on ! ,adju/m5t & ,te/+ ( ,telescopic ,objectives1 by ,t4 ,cook & ,sons1 ,buck+ham ,works1 ,york 7pr9t$ by ,b5 ,johnson & ,co1 ,micklegate1 ,york74 ,?is "w has excell5t photographs ( ! int]f]5ce r+s ( /> images correspond+ to v>i\s defects4 ,x mu/ be und]/ood t ! foll[+ is a m]e sket*4 ,! art w probably h>dly ev] be requir$ 9 laboratory practice1 & ^? :o wi% to con/ruct l>ge telescopes %\ld n be above look+ up ! ref]5ces4 ,! process is naturally divid$ = treatm5t into two p>ts4 7#a7 ,! detection ( errors1 & ! cause ( ^! errors4 7#b7 ,! application ( a rem$y4 7#a7 ,a l5s1 be+ m\nt$ ) its f9al adju/m5ts1 is turn$ on to a />1 :i* mu/ n be too bright1 & %\ld be fairly ov]head4 ,! foll[+ appe>ances may be not$3- ,a4 ,9 focus1 ! /> appe>s z a small disc ) "o or two r+s r\nd x2 inside & outside ( ! focus ! r+s increase 9 numb]1 are r\nd1 conc5tric ) ! disc1 & ! bright & d>k r+s are app>5tly equally wide4 ,! appe>ance inside ! focus exactly resembles t outside :5 all[ance is made = *romatic effects4 ,conclusion3 objective good1 & correctly m\nt$4 ,b4 ,! r+s r\nd ! /> 9 focus are n circul>1 nor is ! /> at ! c5tre ( ! sy/em4 ,9 bad cases ! fr+es are se5 at "o side only4 ,effects exagg]at$ outside & inside ! focus4 ,conclusion3 ! l5s is a/igmatic1 or ! objective is n adju/$ to be co-axial ) ! eyepiece4 ,c4 ,:5 9 focus ! c5tral disc is surr\nd$ by an int]mitt5t diffraction patt]n1 i4e4 = in/ance ! sy/em ( r+s may appe> along1 & ne>1 ?ree or m radii4 ,if ^! %ift :5 ! po9ts ( support ( ! l5s are %ift$1 flexure may be suspect$4 ,d4 ,on obs]v+ inside & outside ! focus1 ! r+s are n equally bright & d>k4 ,?is may be due to uncorrect$ sph]ical ab]ration1 p>ticul>ly to a fault kn[n z zonal ab]ration1 :]e diff]5t zones ( ! l5s h diff]5t foci1 b ea* zone has a def9ite focus4 ,e4 ,irregul> diffraction fr+es po9t to bad anneal+ ( ! glass4 ,?is may be *eck$ by an exam9ation ( ! l5s 9 pol>is$ light4 ,f4 ,if ! disc appe> blurr$ & col\r$1 h[ev] ! focus be adju/$1 incomplete correction = *romatic ab]ration is inf]r$4 ,if 9 addition ! col\r+ is unsymmetrical 79 an extreme case ! /> disc is drawn out to a col\r$ b&71 want ( c5t]+ is to be inf]r$4 ,?is w also %[ itself by ! int]f]5ce fr+es hav+ ! *>act]i/ics describ$ 9 ,c4 7#b7 ,! foll[+ /eps may be tak5 9 apply+ a rem$y3 ,a4 ,! adju/+ screws ( ! cell m\nt+ ! object glass may be work$ until ! be/ result is atta9$2 ?is requires great c>e & pati5ce4 ,any errors left ov] are to be attribut$ to o!r causes ?an ! want ( coll9e>ity ( ! axes ( object glass & eyepiece4 ,b4 ,a/igmatism is detect$ by rotat+ ! object glass or object glass cell4 ,if ! oval fr+es /ill p]si/ & ! long] axis foll[s ! l5s1 a/igmatism may be inf]r$4 ,simil>ly1 by rotat+ "o l5s on ! o!r1 a/igmatism1 or want ( c5t]+ 7q a diff]5t ?+7 may be localis$ to ! l5s4 ,c4 ,! pres5ce ( flexure may be confirm$ by alt]+ ! position ( ! po9ts ( support ) respect to ! eyepiece1 ! l5s ma9ta9+ its orig9al position4 ,! addition ( m po9ts ( support w 9 g5]al r$uce ! ill effects4 ,h[ to get rid ( !m ,i d n "k2 !y are only s]i\s ) l>ge l5ses4 ,d4 ,sph]ical ab]ration may be locat$ by us+ /ops & zonal scre5s1 & obs]v+ ! effect on ! image4 ,sir ,h4 ,grubb det]m9es :e!r any po9t on ! l5s requires to be rais$ or l[]$1 by t\*+ ! glass at t po9t ) a w>m h& or cool+ x by e!r4 ,! effects s produc$ are ! diff]5tial results ( ! *ange ( figure & ( refractive index4 ,by obs]v+ ! effect ( ! heat+ or cool+ ( any "p1 ! op]ator w "k :e!r to raise or l[] t "p1 provid$ t by a suitable prelim9>y exp]im5t he has det]m9$ ! relation betwe5 ! effect produc$ by ! *ange ( figure1 & t due to ! temp]ature v>iation ( ! refractive index4 ,9 g5]al x is suffici5t to consid] ! *ange ( %ape only & neglect ! *ange 9 refractive p[]4 ,e4 ,m>k$ a/igmatism has nev] be5 notic$ by me1 b ,i %\ld ?9k t ! :ole l5s surface w\ld require to be repoli%$ or p]haps regr\nd 9 ?is case4 ,f4 ,to decide 9 :i* surface faults exi/ is n easy4 ,by plac+ a film ( oil betwe5 ! two surfaces ne>ly 9 contact ^! may be easily exam9$4 ,?us a mixture ( nut & almond oil ( ! "r proportion1 to be f\nd by trial1 = ! temp]ature1 w h ! same refractive index z ! cr[n glass1 & w consequ5tly r$uce any errors ( figure 9 ! int]ior cr[n surface1 if prop]ly appli$ betwe5 ! surfaces4 ,simil>ly ! int]ior ( ! fl9t surface may h its imp]fections greatly r$uc$ 9 effect by us+ almond oil alone1 or mix$ ) bisulphide ( c>bon4 ,! out] surfaces1 ,i presume1 mu/ be exam9$ by w>m+ or cool+ ov] suitable areas or zones4 ,! defects be+ detect$1 a matt] requir+ a great deal ( skill & exp]i5ce accord+ to ,sir ,h4 ,grubb1 ! next /ep is to rem$y !m2 & ! rem$ial measures z appli$ to ! glass con/itute ! process ( figur+4 ,!re are two ways ( correct+ local defects1 "o by means ( small pap] or pit* cov]$ tools1 :i* accord+ to ,sir ,h4 ,grubb is dang]\s1 & accord+ to ! exp]i5ce ( ,mr4 ,cook1 & ,i ?9k ( _m ,fr5* opticians1 safe & advantage\s4 ,pit* poli%+ tools are g5]ally us$ = figur+4 ,!y are made by cov]+ a slate back+ ) squ>es ( pit*4 ,! back+ is float$ ) pit* say "o-eigh? ( an in* ?ick4 ,?is is !n scor$ into squ>es by a hot iron rod4 ,! tool1 :ile slightly w>m1 is laid ^u ! l5s surface1 previ\sly slightly sme>$ ) dilute glyc]9e1 until ! pit* takes ! figure ( ! glass4 ,! poli%+ mat]ial is r\ge & wat]4 ,small tools are appli$ locally1 & probably c only be s appli$ ) advantage = grave defects4 ,! o!r me?od is long] & probably saf]4 ,x consi/s 9 furni%+ ! poli%+ tool ) squ>es ( pit* z be=e4 ,^! be+ slightly w>m1 ! l5s is plac$ ^u !m s t !y w fl[ to ! exact figure also z be=e4 ,i presume t ! l5s is to be slightly sme>$ ) glyc]9e1 or "s equival5t1 to keep ! pit* f /ick+4 ,! squ>es are mo/ ?ickly di/ribut$ :]e ! abrasion is mo/ requir$1 i4e4 less pit* is melt$ out by ! iron rod4 ,?is may be supplem5t$ by tak+ advantage ( diff]5ces ( h>dness ( pit*1 mak+ "s squ>es out ( h>d]1 o!rs out ( s(t] pit*4 ,! aim is to produce a poli%+ tool :i* w poli% unequally s z to remove ! glass *iefly f pr$et]m9$ p>ts ( ! l5s surface4 ,! tool is work$ ov] ! surface ( ! l5s by ! poli%+ ma*9e1 & "p ( ! art consi/s 9 adju/+ ! /rokes to assi/ 9 ! production ( ! local v>iations requir$4 ,a s\rce ( difficulty & dang] lies 9 ! fact t ! pit* squ>es are r>ely ( ! same h>dness1 s t "s abrade ! glass m rapidly ?an o!rs4 ,?is is p>ticul>ly likely to occur if ! pit* has be5 ov]heat$4 ,footnote3 ,:5 pit* is heat$ till x evolves bubbles ( gas its h>dness increases ) ! duration ( ! process4 ,! read] mu/ be good en\gh to reg>d ^! rem>ks z ( ! b>e/ possible k9d1 & n int5d$ to convey m ?an a g5]al idea ( ! nature ( ! process ( figur+4 #fh4 ,a few rem>ks on clean+ l5ses w fitt+ly close ?is "p ( ! subject4 ,!re is no ne$ to g beyond ! foll[+ in/ructions giv5 by ,mr4 ,bra%e> 9 ,popul> ,a/ronomy1 #ahid1 :i* are reproduc$ "h v]batim4 ,! writ] does n advise ! use ( ei!r f9e *amois sk91 tissue pap]1 or an old s(t silk h&k]*ief1 nor any o!r su* mat]ial to wipe ! l5ses1 z is usually advis$4 ,x is n1 h[ev]1 ^! wip+ mat]ials t d ! mis*ief1 b ! du/ p>ticles on ! l5ses1 _m ( !m p]haps ( a silici\s nature1 :i* are always h>d] ?an optical glass1 & z ^! p>ticles atta* !mselves to ! wip+ mat]ial !y cut microscopic or great] scrat*es on ! surfaces ( ! objective 9 ! process ( wip+4 ,i write ?is article ) ! hope ( help+ to solve ?is app>5tly difficult problem1 b :i* 9 reality is a v simple "o4 ,let u comm5ce by tak+ ! object glass out ( its cell4 ,take out ! screws t hold ! r+ 9 place1 & lift out ! r+4 ,plac+ ! f+]s ( bo? h&s s z to grasp ! objective on opposite sides1 rev]se ! cell1 & ) ! ?umbs g5tly press ! objective squ>ely out ( ! cell on to a book1 block ( wood1 or any?+ a little less 9 diamet] ?an ! objective1 :i* has _h a cu%ion ( musl9 or any s(t sub/ance laid ^u x4 ,"o p]son c ?us h&le any objective up to #ab in*es 9 diamet]4 ,be=e sep>at+ ! l5ses x %\ld be c>efully not$ h[ !y 7 put toge!r ) relation to ! cell1 & to "o ano!r1 & if !y art n m>k$ !y %\ld be m>k$ on ! edges conspicu\sly ) a h>d lead p5cil1 s t :5 sep>at$ !y may be put toge!r 9 ! same way1 & plac$ 9 ! same relation to ! cell4 ,) only ord9>y precaution ?is %\ld be an easy matt]4 ,sett+ ! objective on edge ! two l5ses may be readily sep>at$4 ,& n[ z to ! clean+ ( ! l5ses4 ,i h1 on r>e occasions1 f\nd ! inn] surfaces ( an object glass cov]$ ) a curi\s film1 n caus$ directly by moi/ure b by ! app>5t oxidation ( ! t9-foil us$ to keep ! l5ses ap>t4 ,a ye> or m ago a #g-;in* objective made by ,mr4 ,cl>k 0 br\ght to me to clean4 ,x _h evid5tly be5 sadly neglect$4 ,! inside ( ! l5ses 7 cov]$ ) su* a film z ,i h m5tion$1 & ,i fe>$ ! glass 0 ru9$4 ,:5 tak5 ap>t x 0 f\nd t ! t9-foil _h oxidis$ totally & _h di/ribut$ itself all ov] ! inn] surfaces4 ,i fe>$ ! result1 b 0 delight$ to f9d t nitric acid & a tuft ( absorb5t cotton cut all ! deposit (f1 leav+ no /a9s aft] hav+ pass$ ?r\gh a subsequ5t wa%+ ) soap & wat]4 ,i m5tion ?is z o!rs may h a simil> case to deal )4 ,= ! ord9>y clean+ ( an objective let a suitable siz$ vessel1 always a wood5 "o1 be ?or\ghly clean$ ) soap & wat]1 !n half fill$ ) clean wat] ab\t ! same temp]ature z ! glass4 ,slight diff]5ces ( temp]ature are ( no mom5t4 ,great diff]5ces are dang]\s 9 l>ge objectives4 ,i usually put a teaspoonful ( ammonia 9 half a pail ( wat]1 & x is well to let a piece ( wa%$ '*eese clo?' lie 9 ! pail1 z !n !re is no dang] if ! l5s slips away f ! h&1 &1 by ! way1 e obs]vatory1 inde$ e amateur own+ a telescope1 %\ld h pl5ty ( '*eese clo?' h&y4 ,x is *eap 7ab\t #c cts4 p] y>d7 & is sup]ior = wip+ purposes to any 'old s(t silk h&k]*ief1' *amois sk91 etc4 ,be=e us+ x h x ?or\ghly wa%$ ) soap & wat]1 !n r9s$ 9 clean wat]1 dri$ & laid away 9 a box or o!r place :]e x c be kept clean4 ,:5 y use a piece to clean an objective ?r[ x away1 x is s *eap y c af=d to d s4 ,if ! l5ses are v dirty or 'du/y1' a tuft ( cotton or a camel's-hair bru% may be us$ to bru% (f ! loose mat]ial be=e plac+ ! l5ses 9 ! wat]1 b no pressure o!r ?an ! weight ( ! cotton or bru% %\ld be us$4 ,! writ] pref]s to use ! palms ( ! h& ) pl5ty ( good soap on !m to rub ! surfaces1 al?\gh ! *eese clo? & ! soap answ]s nicely1 & !re seems to be absolutely no dang] ( scrat*+ :5 us+ ! h&s or ! *eese clo? :5 pl5ty ( wat] is us$2 inde$ :5 ,i wi% to wipe (f ! front surface ( an objective 9 use1 & ! l5s _c well be tak5 out1 ,i fir/ du/ (f ! gross p>ticles & !n use ! *eese clo? ) soap & wat]1 & hav+ gone ov] ! surface g5tly ) "o piece ( clo?1 ?r[ x away & take ano!r1 p]haps a ?ird "o1 & !n :5 ! dirt is1 z x 71 all lift$ up f ! surface1 a piece ( dry *eese clo? w f9i% ! "w1 leav+ a clean brilliant surface1 & no scrat*es ( any k9d4 ,9 wa%+ l>ge objectives 9 wat] ,i g5]ally use a 'tub' & /& ! l5ses on _! edge4 ,:5 ?or\ghly wa%$ !y are tak5 out & laid on a bundle ( *eese clo? & sev]al pieces ( ! same us$ to dry !m4 ,i ?9k x be/ n to leave !m to dra9 dry2 bett] take up all moi/ure ) ! clo?1 & vigor\s rubb+ w d no h>m if ! surfaces h no abrad+ mat]ial on !m4 ,i h yet to injure a glass clean$ 9 ?is way4 ,?is process may seem a r long & t$i\s "o1 b x is n s 9 practice1 & x pays4 ,9 "s places objectives mu/ be frequ5tly clean$1 n only because !y become cov]$ ) an adh]5t du/1 b because t du/ produces s mu* diffus$ light 9 ! field z to ru9 "s k9ds ( telescope "w4 ,mr4 ,hale ( ! ,k5wood ,obs]vatory tells me he _c d any good prom95ce photography unless 8 objective has a clean surface2 inde$ e obs]v] ( fa9t objects or delicate planet>y m>k+s kn[s full well ! value ( a d>k field free f diffus$ light4 ,! object-glass mak] uses 8 be/ ef=ts to produce ! mo/ p]fect poli% on 8 l5ses1 aside f ! accuracy ( ! curves1 bo? = high light value & fre$om f diffus$ light 9 ! field1 & if ! surfaces are all[$ to become cov]$ ) du/1 8 good "w c\nts = little4 ,if only ! front surface ne$s clean+1 ! me?od ( clean+ ) *eese clo?1 soap & wat]1 z describ$ above1 answ]s v well1 b always ?r[ away ! fir/ &1 if necess>y1 ! second clo?1 !n wipe dry ) a ?ird or f\r? clo?2 b if ! surfaces all ne$ clean+ ,i "k ( no bett] me?od ?an t ( tak+ ! objective out ( its cell1 always us+ abundance ( soap & wat]1 & keep 9 a good humor4 #fi4 ,! ,prep>ation ( ,flat ,surfaces ( ,rock ,salt4 ,! prelim9>y gr9d+ is accompli%$ z 9 ! case ( glass1 except t x goes on va/ly fa/]4 ,! poli%+ process is ! only "p ( ! op]ation :i* pres5ts any difficulty4 ,! foll[+ is an extract f a pap] on ! subject1 by ,mr4 ,j4 ,a4 ,bra%e>1 ,pittsburg1 ,pa1 ,u4,s4,a1 f ! ,proce$+s ( ! ,am]ican ,association = ! ,advancem5t ( ,sci5ce1 #ahhe4 ,practically ! same me?od 0 %[n me by ,mr4 ,cook "s ye>s e>li]1 s t ,i c endorse all t ,mr4 ,bra%e> says1 ) ! foll[+ exceptions4 ,we consid] t = small salt surfaces ! pit* is bett] scor$ into squ>es ?an provid$ ) ! holes recomm5d$ by ,mr4 ,bra%e>4 ,mr4 ,bra%e>'s in/ructions are z foll[s4 ,aft] allud+ to ! difficulty ( dry+ ! poli%$ salt surface--:i* is ( c\rse wet--,mr4 ,bra%e> says3- ,happily ,i h no tr\ble 9 ?is respect n[1 & z my me?od is easily c>ri$ out by any physici/ :o desires to "w ) rock salt surfaces1 x gives me pleasure to expla9 x4 ,= poli%+ a prism ,i make an ord9>y pit* b$ ( ab\t two & "o-half or ?ree times ! area ( ! surface ( ! prism to be poli%$4 ,:ile ! pit* is /ill w>m ,i press ^u x any approximately flat surface1 su* z a piece ( ord9>y plate glass4 ,! pit* b$ is !n cool$ by a /ream ( wat]1 & conical holes are !n drill$ 9 ! pit* ) an ord9>y c\nt] s9k bit1 say "o-qu>t] ( an in* 9 diamet]1 & at int]vals ( half an in* ov] ! entire surface4 ,?is is done to relieve ! atmosph]ic pressure 9 ! f9al "w4 ,! upp] surface ( ! pit* is n[ v slightly w>m$ & a true plane surface 7usually a glass "o1 prep>$ by gr9d+ & poli%+ ?ree surfaces 9 ! ord9>y way1 previ\sly wett$7 is press$ ^u x until ! pit* surface becomes an approximately true plane itself4 ,=tunately1 mod]ately h>d pit* reta9s its figure q p]si/5tly ?r\gh %ort p]iods & small *anges ( temp]ature1 & x always pays to sp5d a little "t 9 ! prep>ation ( ! pit* b$4 ,! poli%] be+ n[ ready1 a v small quantity ( r\ge & wat] is tak5 ^u a f9e sponge & equally di/ribut$ ov] its surface4 ,! previ\sly gr\nd & f9$ salt surface 7?is "w is done ! same z 9 glass work+7 is n[ plac$ ^u ! poli%] & motion in/antly set up 9 diametral /rokes4 ,i usually walk ar\nd ! poli%] :ile work+ a surface4 ,x is well to note t motion mu/ be con/ant1 = a mom5t's re/ is fatal to good results1 = ! reason t ! surface is quickly eat5 away1 & irregul>ly s1 ow+ to ! holes t are 9 ! pit* b$4 ,n[ comes ! mo/ important "p ( ?is me?od4 ,aft] a few m9utes' "w ! moi/ure w beg9 to evaporate q rapidly4 ,no new application ( wat] is to be made1 b a c>eful wat* mu/ be kept ^u ! pit* b$1 & z ! la/ ve/ige ( moi/ure disappe>s ! prism is to be slipp$ (f ! poli%] 9 a p]fectly horizontal direction1 & if ! "w has be5 well done1 a clean1 bright1 & dry surface is ! result4 ,! surface is n[ te/$ by ! well-kn[n me?od ( int]f]5ce f a p]fect glass te/ plate 7see ,fig4 #agh74 ,if an error ( concavity pres5ts itself ! process ( poli%+ is gone ov] aga91 us+ %ort diametral /rokes4 ,if ! error is "o ( convexity1 ! poli%+ /rokes are to be made along ! *ords1 ext5d+ ov] ! edge ( ! poli%]4 ,! "o ess5tial feature ( ?is me?od is ! fact t ! surface is wip$ dry 9 ! f9al /rokes1 ?us gett+ rid ( ! "o great difficulty ( pit* poli%+1 a me?od und\bt$ly f> sup]ior to t ( poli%+ on broadclo?4 ,if 9 ! f9al /rokes ! surface is n q clean$ ,i usually brea! ^u ! pit* b$1 & ?us by cond5sation place en\gh moi/ure ^u x to give a few m /rokes1 f9i%+ j ! same z be=e4 ,9 t5 m9utes ,i h poli%$ prisms ( rock salt 9 ?is mann] t h n only %[n ! ,d l9e d\ble1 b ,pr(essor ,langley has in=m$ me t 8 assi/ant1 ,mr4 ,keel] 7,j4 ,e471 has se5 ! nickel l9e cle>ly betwe5 ! ,d l9es4 ,?is speaks = ! sup]iority ( ! surfaces ov] ^? poli%$ on broadclo?4 ,9 poli%+ prisms ,i pref] to "w !m on top ( ! poli%]1 z !y c be easily held1 b z x is difficult to hold l5ses or planes 9 ?is way )\t injur+ ! surfaces1 ,i usually support !m 9 a block ( s(t wood1 turn$ s z to t\* only at _! edges1 & "w ! poli%] ov] !m4 ,?\gh x takes consid]able practice to succe$ at fir/1 ! results are s good t x well repays ! few h\rs' "w x requires to ma/] ! few difficulties x pres5ts4 ,fig4 #eh4 #gj4 ,ca/+ ,specula = ,mirrors4 ,accord+ to ,sir ,h4 ,grubb 7loc4 cit47 ! be/ alloy is made ( f\r atoms ( copp] & "o ( t92 ?is gives by weight1 copp] #beb1 t9 #aag4h4 ,! copp] is melt$ fir/ 9 a plumbago crucible2 ! t9 is add$ gradually4 ,( c\rse1 9 ! process ( melt+1 ev5 ?\gh a little f9e *>coal be spr9kl$ ov] ! copp]1 "s loss ( t metal w occur f oxidation4 ,x is conv5i5t 9 practice1 !re=e to res]ve a portion ( ! t9 & te/ ! cont5ts ( ! crucible by lift+ a little ( ! alloy out & exam9+ x4 ,! foll[+ indications may be not$3 ,:5 ! copp] is 9 excess ! t9t ( ! alloy is slightly r$1 & ! /ructure1 z %[n at a fractur$ surface1 is co>sely cry/all9e4 ,z ! prop] proportions are m ne>ly atta9$1 ! cry/all9e /ructure becomes f9]1 ! col\r :it]1 & ! cry/als bright]4 ,! alloy is ready = use :5 ! maximum brightness is atta9$ & ! gra9 is f9e4 ,if too mu* t9 be add$1 ! lu/re dim9i%es4 ,! correct proportion is1 !re=e1 atta9$ :5 a fur!r small addition ( t9 produces no app>5t increase ( brightness or f95ess ( gra94 ,ab\t ?ree-qu>t]s ( ! t9 may be add$ at fir/1 & ! o!r qu>t] add$ ) te/+ z describ$4 ,! alloy is all[$ to cool until on skimm+ ! surface ! metal appe>s bright & rema9s s )\t los+ its lu/re by oxidation = a s5sible "t2 x w /ill be q r$-hot4 ,fig4 #ei4 ,fig4 #fj4 ,z ! speculum alloy is too difficult to "w ) ord9>y tools1 x is be/ to ca/ ! speculum ( exactly ! requir$ %ape & size4 ,?is is done by means ( a r+ ( iron turn$ inside 7& out7 & on "o edge4 ,?is r+ is laid on a plate ( figur$ iron1 & be=e ! metal is p\r$ ! plate 7,g7 7,figs #ei & #fa7 is heat$ to1 say1 #cjj ,c4 ,9 ord] to avoid ! pres5ce ( oxide z f> z possible1 ! foll[+ arrangem5ts = p\r+ are made4 ,a portion ( ! l[] surface ( ! r+ is remov$ by radial fil+ until a not* equal to1 say1 "o-tw5tie? ( ! :ole circumf]5ce is produc$4 ,?is is cut to an axial dep? (1 say1 half an in*4 ,a b> ( iron is !n dovetail$ loosely into ! not* 7,fig4 #fj1 ,b71 s t x w re/ on ! iron plate1 & half fill ! not*4 ,! ap]ture ?us left =ms ! port ( +ress = ! hot metal 7see ,fig4 #fa1 ,m74 ,a bit ( %eet iron is atta*$ to ! upp] surface ( ! r+1 & lies z a sort ( flap1 %ap$ l a deep %ovel1 aga9/ ! outside ( ! r+ ov]hang+ ! port 7,figs4 #ei & #fa at ,f74 ,?is flap does n q rea* ! iron plate1 & its sides are b5t s z to be 9 contact ) ! r+4 ,a portion ( a small] r+ is !n appli$ 9 su* a mann] z to =m a p\r+ lip or pool on ! outside ( ! ma9 r+ at ,e1 & ! metal c only get into ! ma9 r+ by pass+ "u ! edge ( ! flap & up ?r\gh ! port4 ,?is =ms an effici5t skimm+ arrangem5t4 ,! process ( ca/+ is c>ri$ out by p\r+ /eadily into ! lip4 ,to avoid air bubbles x is conv5i5t to cause ! metal to spread sl[ly ov] ! *ill1 & ,mr4 ,nasmy?'s me?od ( accompli%+ ?is is %[n 9 ! figure 7#fa74 ,! *ill re/s on ?ree p9s1 ,a ,b ,c 7,figs4 #ei & #fa74 ,be=e p\r+ beg9s ! *ill is tilt$ up (f ,c by means ( ! c\nt]poise ,d1 :i* is insuffici5t to tilt x aft] ! speculum is p\r$4 ,x is important t ! *ill %\ld be horizontal at ! close ( ! op]ation1 9 ord] t ! speculum may be ( ev5 ?ickness ?r\gh\t4 ,?is is not$ by means ( levels plac$ on ! r+ 7at ,k = in/ance74 ,fig4 #fa4 ,?is app>atus may appe> unnecess>ily complex1 b x is wor? :ile to set x up1 = x makes ! op]ation ( ca/+ a speculum fairly c]ta94 ,if ! metal is at ! "r temp]ature x w =m a uni=mly liquid disc inside ! r+4 ,! mass sets almo/ directly1 & z soon z ?is occurs x is pu%$ to ! edge ( ! plate & ! metal 9 ! lip brok5 (f by a sm>t upw>d tap ) a hamm]4 ,! dovetail$ bit ( iron is knock$ d[nw>ds & falls (f1 & ! r+ may !n be lift$ cle> ( ! ca/+4 ,! object ( ! dovetail w n[ be und]/ood1 = )\t x !re is great risk ( break+ into ! speculum 9 knock+ ! tail (f4 ,a box ( q dry sawdu/ is prep>$ 9 read9ess = ! process ( anneal+ be=e ! speculum is ca/4 ,! box mu/ be a s\nd wood5 or metal box1 & mu/ be approximately air-tight4 ,= a speculum a foot 9 diamet] ! box mu/ measure at lea/ #c feet bo? ways 9 plan1 & be #b feet #f in*es deep4 ,half ! sawdu/ is 9 ! box & is well press$ d[n s z to half fill x4 ,! o!r half mu/ be conv5i5tly ready to h&4 ,z soon z possible aft] ca/+1 ! speculum is ?r[n into ! box1 cov]$ ov] ) ! sawdu/1 & ! lid is put on4 ,! object 9 hav+ ! box ne>ly air-tight is to avoid air-curr5ts1 :i* w\ld increase ! rate ( cool+4 ,a speculum a foot 9 diamet] may conv5i5tly take ab\t ?ree days to anneal1 & %\ld be s5sibly w>m :5 ! box is op5$ on ! f\r? day4 ,= l>g] sizes long] times w be requir$4 ,we w say t ! sawdu/ ?ickness on ea* side mu/ be proportional to ! dim5sions ( ! speculum1 or may ev5 increase fa/] ) advantage if "t is ( no mom5t4 ,! process ( anneal+ may be consid]$ successful if ! disc does n fly to pieces 9 work+2 x is to be work$ on ! *ill$ side4 ,! object ( giv+ ! *ill ! approximate c\nt]p>t =m w n[ appe>2 x saves "s r\gh gr9d+1 & causes ! f9i%$ surface to be m homog5e\s ?an x w\ld be if ! c5tre 7 sunk by gr9d+ ?r\gh ! *ill$ surface4 ,9 #ahhi ,i le>n$ f ,mr4 ,s*neid]1 ,pr(essor ,r[-l&'s assi/ant at ,baltimore1 t 9 ca/+ specula = concave grat+s a good deal ( tr\ble _h be5 sav$ by c>ry+ out ! op]ation 9 an atmosph]e consi/+ mo/ly ( coal gas4 ,x 0 claim$ t 9 ?is way ! pres5ce ( specks ( oxide 0 avoid$4 ,i did n see ! process 9 op]ation1 b ! results atta9$ are kn[n & admir$ by all exp]im5t]s4 #ga4 ,gr9d+ & poli%+ ,specula4 ,! r\gh gr9d+ is accompli%$ by means ( a lead tool & co>se em]y2 ! size ( gra9 may be su* z w pass a sieve ( #fj ?reads to ! in*4 ,! process ( gr9d+ is q simil> to t previ\sly describ$1 b x goes on comp>atively quickly4 ,! r\gh gr9d+ is *eck$ by ! sph]omet]1 & is int]rupt$ :5 t in/rum5t gives accordant & correct measurem5ts all ov] ! surface4 ,! f9e gr9d+ may be proce$$ ) by means ( a glass-fac$ tool z be=e describ$1 or ! lab\r may be r$uc$ 9 ! foll[+ mann]4 ,a slate tool1 :i* mu/ be free f gre5 spots 7a s\rce ( unev5 h>dness71 is prep>$1 & ?is is br\ght ne>ly to ! curvature ( ! r\ghly gr\nd speculum1 by turn+ or o!rwise4 ,x is f9i%$ on ! speculum itself ) a little fl\r ( em]y4 ,! f9e gr9d+ is !n c>ri$ on by means ( slate du/ & wat]1 ! slate tool be+ ! gr9d]4 ,! tool is1 ( c\rse1 scor$ into squ>es on ! surface4 ,if ! ca/+ process has be5 c>ri$ out successfully1 ! r\gh gr9d+ may take1 say six h\rs1 & ! f9e gr9d+ say ?irty h\rs = a disc a foot 9 diamet]4 ,! greate/ s\rce ( tr\ble is want ( homog5eity 9 ! ca/+1 z evid5c$ by bl[holes1 etc4 ,9 g5]al1 ! %orte/ way is to disc>d ! disc & />t afre% if !re is any s]i\s want ( p]fection 9 ! cont9uity or homog5eity ( ! metal4 ,fig4 #fb4 ,! f9ely gr\nd surface mu/1 ( c\rse1 be app>5tly correct 9 s f> z a sph]omet] 7) #c in*es betwe5 ! legs = a disc #a foot 9 diamet]7 w %[4 ,poli%+ & figur+ are c>ri$ out simultane\sly4 ,half an h\r's poli%+ ) a slate-back$ pit* tool & r\ge & wat] w enable an optical te/ to be made4 ,! mo/ conv5i5t te/ is t ( ,f\cault1 a simple appliance = ! purpose be+ %[n 9 ! figure 7#fb74 ,x ess5tially consi/s ( a small lamp surr\nd$ by an opaque *imney 7,a7 ?r\gh :i* a m9ute ap]ture 7p9-hole7 is made4 ,a small l5s may be us$1 ( v great curvature1 or ev5 a transp>5t m>ble to ?r[ an image ( ! flame on ! p9-hole4 ,a scre5 7,b7 is plac$ close to ! s\rce1 & is provid$ ) a rock+ or tilt+ motion 7,c7 9 its own plane4 ,! s\rce & scre5 are p>tly indep5d5t1 & ea* is provid$ ) a f9e adju/m5t :i* s]ves to place x 9 position ne> ! c5tre ( curvature4 ,! scre5 is s close to ! p9-hole 9 fact t bo? ! s\rce & a po9t on ! edge ( ! scre5 may be said to be at ! c5tre ( curvature ( ! mirror4 ,! mirror is tempor>ily m\nt$ s z to h its axis horizontal1 9 a cell> or o!r place ( uni=m temp]ature4 ,! f9al focuss+ to ! c5tre ( curvature is made by ! f9e adju/m5t screws2 ! image may be receiv$ on a bit ( pap] plac$ on ! scre5 & ov]lapp+ ! edge ne>e/ ! s\rce4 ,! screws are work$ till ! image has its smalle/ dim5sion & is bisect$ by ! edge ( ! scre54 ,! te/ consi/s 9 obs]v+ ! appe>ance ( ! mirror surface :ile ! scre5 is tilt$ to cut (f ! light1 z se5 by an eye plac$ at ! edge ( ! scre51 a peephole or eye l5s be+ provid$ to facilitate plac+ ! eye 9 a correct position4 ,! scre5 screws are work$ s z to gradually cut (f ! light1 & ! obs]v] notes ! appe>ance ( ! mirror surface4 ,if ! curves are p]fect & sph]ical1 ! transition f complete illum9ation to d>kness w be abrupt1 & no "p ( ! mirror w rema9 illum9at$ aft] ! re/4 ,= a/ronomical purposes a p>abolic mirror is requir$4 ,9 ?is case ! disc may be p>tially scre5$ by zonal scre5s1 & ! position ( ! image = diff]5t zones not$2 ! correctness or o!rwise ( ! curvature may !n be asc]ta9$ by calculation4 ,a %ort] way is to place ! s\rce j outside ! focus1 to be f\nd by trial1 & !n1 mov+ ! ext9ction scre5 7n[ a sep>ate appliance7 to1 say1 five times ! radius ( curvature away1 :]e ! image %\ld n[ appe>1 ! sudd5ness ( ext9ction may be inve/igat$4 ,?is1 ( c\rse1 involves a correspond+ modification ( ! app>atus4 ,:e!r ! te/s indicate t a deep5+ ( ! ,c5tre1 i4e4 increase ( ! curvature1 or a flatt5+ ( ! edges is requir$1 at lea/ two rem$ial processes are available4 ,! *isel & mallet me?od ( alt]+ ! size ( ! pit*1 squ>es ( ! poli%] may be employ$1 or pap] or small pit* tools may be us$ to deep5 ! c5tre4 ,! *isel & mallet me?od m]ely consi/s 9 remov+ pit* squ>es f a uni=mly divid$ tool surface by means ( ! in/rum5ts m5tion$4 ,?is removal is effect$ at ^? po9ts at :i* ! abrasion requires to be r$uc$4 ,:5 "s practice is atta9$1 ,i und]/& t x is usual to try = a p>abolic =m at once1 z soon z ! poli%+ comm5ces4 ,?is is done by divid+ ! pit* surface by ,v-%ap$ grooves1 ! sides ( ! grooves be+ radii ( ! circul> surface1 s t ! c5tral p>ts ( ! mirror get mo/ ( ! poli%+ action4 ,if pap] tools are us$ !y mu/ n be all[$ mu* ov]hang1 or ! edges ( ! mirror betray ! effects ( pap] ela/icity4 ,mo/ op]ators s9k ! middle1 b ! late ,mr4 ,lassell1 a mo/ accompli%$ work]1 always atta9$ ! p>abolic =m by r$uc+ ! curvature ( ! edges ( a sph]ical mirror4 #gb4 ,prep>ation ( ,flat ,surfaces4 ,z ,sir ,h4 ,grubb has po9t$ out1 ?is op]ation only diff]s f ^? previ\sly describ$ 9 t an additional condition has to be satisfi$4 ,?is condition ref]s to ! mean curvature1 :i* mu/ be exact 79 ! case ( flats x is ( c\rse z]o7 to a degree :i* is q unnecess>y 9 ! manufacture ( mirrors or l5ses4 ,a little consid]ation w %[ t to get a surface flat ! mo/ /raight=w>d me?od is to c>ry out ! necess>y & suffici5t condition = ?ree surfaces to fit ea* o!r imp>tially4 ,if !y ea* fit ea* o!r1 !y mu/ cle>ly all be flat4 ,to c>ry out ! process ( produc+ a flat surface1 !re=e1 two tools are made1 & ! glass or speculum is gr\nd fir/ on "o & !n on ! o!r1 ! tools be+ kept 9 fit by occasional mutual gr9d+4 ,! gr9d+ & poli%+ g on z usual4 ,if pap] is employ$1 c>e mu/ be tak5 t ! poli%] is ab\t ! same size z ! object to be poli%$4 ,!re is a slight t5d5cy to poli% mo/ at ! edges2 b if ! sweeps are ( ! "r %ape & size1 ?is may be correct$ approximately4 ,! be/ surfaces :i* h come "u my notice are ^? prep>$ z te/ surfaces by ,mr4 ,bra%e> ( ,alleghany1 ,pa1 ,u4,s4,a4 ,^! ,i believe to be pit* poli%$4 ,a pit* b$ is prep>$1 ,i presume1 9 a mann] simil> to t describ$ = rocksalt surfaces2 b ! work+ ( ! glass is an imm5se art1 & "o :i* ,i believe--if "o may judge by results--is only kn[n to ,mr4 ,bra%e>4 ,9 g5]al1 ! effect ( poli%+ w be to produce a convex or concave surface1 q good en\gh = mo/ purposes1 b di/9ctly faulty :5 te/$ by ! int]f]5ce fr+es produc$ ) ! aid ( ! te/ plate4 ,! foll[+ in=mation !re=e--:i* ,i draw f ,mr4 ',cook--w n enable a /ud5t to emulate ,mr4 ,bra%e>1 b w und\bt$ly help him to get a v mu* bett] surface ?an he usually buys at a high price1 z exhibit$ on a spectroscope prism4 ,! only diff]5ce betwe5 ?is process & ! "o describ$ = poli%+ l5ses1 lies 9 ! fact t ! r\ge is put into ! pap] surface :ile ! latt] is wet ) a dilute gum mucilage4 ,x is ( c\rse assum$ t ! object & ! two tools h be5 f9ely gr\nd & fit ea* o!r imp>tially4 ,! pap] is rubb$ ov] ) r\ge & weak gum wat]4 ,! tool1 :5 dry1 is appli$ to ! flat gr\nd surface 7( ! object71 & is scrap$ ) ! ?ree-corn]$ file *isel z =m]ly describ$4 ,?is process mu/ be v c>efully c>ri$ out4 ,! pap] mu/ be ( ! quality m5tion$1 or may ev5 be ?9n] & h>d]4 ,! cross /rokes %\ld be m employ$ ?an 9 ! case ( ! curv$ surfaces4 ,a good deal w dep5d on ! me?od employ$ = support+ ! "w2 x is 9 g5]al bett] to support ! tool1 :i* may h a slate back+ ( any desir$ ?ickness1 :]eby ! difficulty result+ f /ra9s is r$uc$4 ,! "w mu/ be m\nt$ 9 su* a way z to m9imise ! effect ( *anges ( temp]ature4 ,if a pit* b$ is select$1 ,mr4 ,bra%e>'s in/ructions = rock salt may be foll[$1 )1 ( c\rse1 ! obvi\s necess>y modifications4 ,see also next section4 #gc4 ,poli%+ ,flat ,surfaces on ,glass or on ,speculum ,metal4 ,! above process may be employ$ = speculum metal1 or pit* may be us$4 ,9 ! latt] case a fre% tool mu/ be prep>$ e h\r or s1 because ! metal beg9s to /rip & leave bits on ! poli%]2 ?is causes a c]ta9 am\nt ( scrat*+ to take place4 ,z aga9/ ?is disadvantage1 ! process ( poli%+1 9 s f> z ! /ate ( ! surface is conc]n$1 ne$ n take an h\r if ! f9e gr9d+ has be5 well done4 ,= ! f9e/ "w *anges ( temp]ature1 z 9 ! case ( glass1 cause a good deal ( tr\ble1 & ! op]ator mu/ try to arrange 8 me?od ( hold+ ! object s z to give rise to ! lea/ possible communication ( heat f ! h&4 ,! p>tial ela/icity ( pap]1 :i* is its defect z a poli%+ back+1 is1 ,i believe1 p>tly c\nt]balanc$ by ! difficulty ( =m+ ) pit* an exact c\nt]p>t tool )\t introduc+ a s]i\s rise ( temp]ature 7i4e4 w>m+ ! pit*74 ,! rate ( subsid5ce ( ! latt] is v sl[ at temp]atures :]e x is h>d en\gh to "w reliably z a poli%]4 ,a /ud5t int]e/$ 9 ! matt] ( flat surfaces w d well to read an acc\nt ( ,"l ,rayleigh's "w on ! subject1 ,nature1 vol4 xlviii1 #ahic1 pp4 #bab1 #ebf 7or ,b4 ,a4 ,reports1 #ahic74 ,9 ! fir/ ( ^! communications ,"l ,rayleigh describes ! me?od ( us+ te/ plates1 & %[s h[ to obta9 ! int]f]5ce fr+es 9 ! cle>e/ mann]4 ,= ! ord9>y optician a d>k room & a soda flame af=d all requisite in=mation2 & if a p]son succe$s 9 mak+ ?ree glass discs1 say #f in*es 9 diamet]1 s flat t1 :5 sup]pos$ 9 any mann]1 ! int]f]5ce fr+es are p>allel & equidi/ant1 ev5 to ! r\ghe/ obs]vation1 he has no?+ to le>n f any book ev] writt5 on glass poli%+4 ,"l ,rayleigh has also %[n h[ to use ! free clean surface ( wat] z a natural te/ plate4 ,s9ce ! above 0 writt5 ! foll[+ details ( 8 exact c\rse ( proc$ure h be5 s5t to me by ,mr4 ,bra%e>1 & ,i h]eby t5d] my ?anks3- ,x really takes ye>s to "k j :at to d :5 y rea* t po9t :]e ano!r t\* ei!r gives y ! mo/ p]fect results atta9able1 or ru9s ! "w y h already done4 ,x has tak5 u a long "t to f9d out h[ to make a flat surface1 & :5 we 7 call$ ^u to make ! tw5ty-eight plane & p>allel surfaces = ! inve/igation ( ! value ( ! metre ( ! int]national /&>d1 e "o ( :i* requir$ an accuracy ( "o-tw5tie? ( a wave l5g?1 we _h a difficult task to p]=m4 ,h[ev]1 x 0 f\nd t e surface _h ! desir$ accuracy1 & "s ( !m w5t f> beyond x4 ,x is an advantage 9 mak+ flat surfaces to make m ?an "o at a "t2 x is bett] to make at lea/ ?ree1 & 9 fact we always gr9d & 'f9e' ?ree toge!r4 ,9 mak+ speculum plates we get up t5 or twelve at once on ! lead lap4 ,^! speculum plates we c te/ z we g on by means ( our te/ plane until we get !m ne>ly flat4 ,9 poli%+ !m we fir/ make q a h>d poli%]1 =m+ x on a l>ge te/ plane t is v ne>ly correct4 ,we !n poli% a :ile on "o surface & te/ x1 !n on a second & te/ x1 & aft] a :ile we accumulate plates t are slightly concave & slightly convex4 ,by work+ ^u ^! alt]nately ) ! same poli%]1 we f9ally get our poli%] into su* %ape t x approximates m & m to a flat surface1 & ) extreme c>e & sl[ proc$ure we f9ally atta9 ! results desir$4 ,all our flats are poli%$ on a ma*9e :i* has b little virtue 9 itself1 unmix$ ) bra9s4 ,any ma*9e giv+ a /raight diametrical /roke w answ] ! purpose4 ,! glass %\ld be m\nt$ s z to be p]fectly free to move 9 e direction--t is to say1 p]fectly uncon/ra9$4 ,we m\nt all our flats on a piece ( body ,brussels c>pet1 s t e individual "p ( ! wo( acts z a yield+ spr+4 ,! flats are held 9 place by wood5 clamps at ! edges1 :i* nev] t\*1 b all[ ! bits ( glass or metal to move sl[ly ar\nd if !y are circul>2 if !y are rectangul> we all[ !m to tumble ab\t z !y please )9 ! frame hold+ !m4 ,= mak+ speculum metal plates ei!r plane or concave we use poli%]s s h>d t !y scrat* ! metal all ov] ! surface ) f9e microscopic scrat*es4 ,we always "w = figure1 & :5 we get a h>d poli%] t is 9 prop] %ape1 we c d ev] s _m surfaces ) x if ! environm5ts ( temp]ature are all "r4 ,if we h fifty speculum flats to make1 & we rec5tly made ?ree times t numb]1 we get !m all ready & ( accurate surface ) ! h>d poli%]4 ,!n we prep>e a v s(t poli%]1 easily ind5t$ :5 cold ) ! ?umb nail4 ,a drop ( r\ge & ab\t ?ree drops ( wat] are put on ! plate1 & ) ! s(t poli%] ab\t "o m9ute suffices to clean up all ! scrat*es & leave a beautiful black poli% on ! metal4 ,?is f9al t\* is giv5 by h&2 if we d n get ! poli% 9 a few m9utes ! surface is g5]ally ru9$ = %ape1 & we h to resort to ! h>d poli%] aga94 ,i assure y t no?+ b pati5ce & p]sev]ance w ma/] ! difficulty t "o has to enc\nt]1 b ) ^! two elem5ts 'y are b\nd to get !re4' ,,*apt] ,,iii ,,miscellane\s ,,processes #gd4 ,coat+ ,glass ) ,alum9ium & ,sold]+ ,alum9ium4 ,a process ( coat+ glass ) alum9ium has be5 lately discov]$1 :i*1 if ,i mi/ake n1 may be ( imm5se s]vice 9 special cases :]e a /rongly adh]5t deposit is requir$4 ,my att5tion 0 fir/ attract$ to ! matt] by an article 9 ! ,ar*ives des ,sci5ces physiques et naturelles de ,g5ve1 #ahid1 by ,m4 ,m>got4 ,x appe>s t clean alum9ium us$ z a p5cil w leave a m>k on clean damp glass4 ,if1 in/ead ( a p5cil1 a small :eel ( alum9ium--say z big z a halfp5ny & ?ree times z ?ick--is rotat$ on ! la!1 & a piece ( glass press$ aga9/ x1 ! alum9ium w =m an adh]5t1 ?\gh n v cont9u\s coat+ on ! glass4 ,work+ ) a disc ( ! size describ$ rotat+ ab\t z fa/ z = brass-turn+1 ,i cov]$ ab\t two squ>e in*es ( glass surface 9 ab\t five m9utes4 ,! deposit 0 ( v unev5 ?ickness1 b 0 ne>ly all ?ick en\gh to be s5sibly opaque4 ,by burni%+ ! brilliance is improv$ 7,i us$ an agate burni%] & oil71 b a little ( ! alum9ium is rubb$ (f4 ,! fact t ! burni%] does n entirely remove x is a sign ( ! /r5g? ( ! adh]5ce :i* exi/s betwe5 ! alum9ium & ! glass4 ,9 mak+ ! exp]im5t1 c>e mu/ be tak5 to h ! glass q clean--or at all ev5ts free f grease--9 ord] to obta9 ! be/ results4 ,m4 ,m>got has contribut$ fur!r in=mation to ! ,ar*ives des ,sci5ces physiques et naturelles 7,febru>y #ahie74 ,he f9ds t adh]5ce betwe5 alum9ium & glass is promot$ by du/+ ! glass ) p[d]s1 su* z r\ge4 ,!re is no d\bt t a consid]able improvem5t is effect$ 9 ?is way2 bo? r\ge & alum9a h 9 my h&s greatly increas$ ! facility ) :i* ! alum9ium is deposit$4 ,m4 ,m>got f9ds t z9c & magnesium resemble alum9ium 9 hav+ prop]ties ( adh]5ce to glass1 &1 :at is m1 c>ry ?is prop]ty into _! alloys ) t94 ,?us an alloy ( z9c & t9 9 ! proportions ( ab\t #ib p] c5t t9 & #h p] c5t z9c may be melt$ on absolutely clean glass1 & w adh]e /rongly to x if well rubb$ by an asbe/os crayon4 ,a happy inspiration 0 to try :e!r ^! alloys w\ld1 "u simil> circum/ances1 adh]e to alum9ium itself1 & a trial %[$ t ?is 0 inde$ ! case1 provid$ t bo? ! alum9ium & alloy are scrupul\sly clean & free f oxide4 ,9 ?is way ,m4 ,m>got has solv$ ! problem ( sold]+ alum9ium4 ,i h satisfi$ myself by trial ( ! p]fect ease & absolute success ( ?is me?od4 ,! alloy ( z9c & t9 9 ! proportions above m5tion$ is =m$ at ! l[e/ possible temp]ature by melt+ ! con/itu5ts toge!r4 ,x is !n p\r$ s z to =m ?9 /icks4 ,! alum9ium is c>efully clean$ by rubb+ ) a cuttle bone1 or f9e s&1 & /rong w>m pota%4 ,x is !n wa%$ 9 wat] & dri$ ) a clean clo?4 ,! alum9ium is n[ held ov] a clean flame & heat$ till x w melt ! sold] :i* is rubb$ aga9/ x4 ,! sold] /icks at once1 especially if rubb$ ) ano!r bit ( alum9ium 7an alum9ium sold]+ bit7 simil>ly coat$4 ,to sold] two bits ( alum9ium toge!r x is only necess>y to t9 ! bits by ?is process & !n sweat !m toge!r4 ,! same process applies p]fectly to alum9ium caus$ to adh]e to glass by ! previ\sly m5tion$ process1 & enables /rong sold]$ contacts to be made to glass4 ,9 "o case1 :ile ,i 0 te/+ ! me?od1 ! adhesion 0 s /rong t ! sold] on contract+ :ile cool+ actually *ipp$ ! surface clean (f ! glass4 ,9 ord] to get ov] ?is ,i h endeav\r$ to s(t5 ! sold] by mix+ 9 a little ( ! fusible metal m]cury amalgam2 & ?\gh ?is prev5ts ! glass f be+ s mu* /ra9$1 x r$uces ! adh]5ce ( ! sold]4 ,x is a com=t to be able to sold] alum9ium aft] work+ = s _m ye>s by way ( electroplat+1 or fil+ "u sold]4 ,an alt]native me?od ( sold]+ alum9ium w be describ$ :5 ! electroplat+ ( alum9ium is discuss$1 #ach4 ,gild+ ,glass4 ,9 look+ ov] "s volumes ( ! ,j\rnal fu] praktis*e ,*emie1 ,i came across a me?od ( gild+ glass due to ,boettg] 7,j\rn4 f4 prakt4 ,*em4 #ajc1 p4 #dad74 ,aft] _m trials ,i believe ,i am 9 a position to give def9ite in/ructions z to ! be/ way ( c>ry+ out ?is r tr\blesome op]ation4 ,! films ( gold obta9$ by ! process are v ?ick1 & ! appe>ance ( ! gold exce$+ly f9e4 ,! difficulty lies 9 ! exact apportionm5t ( ! r$uc+ solution4 ,if too mu* ( ! r$uc+ solution be add$1 ! gold deposits 9 a f9e mud1 & no coat+ is obta9$4 ,if1 on ! o!r h&1 too little ( ! r$uc+ solution be add$1 little or no gold is deposit$4 ,! secret ( success turns on exactly hitt+ ! prop] proportions4 ,! r$uc+ solution consi/s ( a mixture ( aldehyde & glucose1 & ! difficulty ,i h _h 9 foll[+ ,boettg]'s in/ructions arose f 8 specify+ comm]cial aldehyde ( a c]ta9 specific gravity :i* x 0 impossible to reproduce4 ,i did n wi% to specify pure aldehyde1 :i* is n v easily got or /or$1 & consequ5tly ,i h _h to det]m9e a crit]ion z to :5 ! proportion ( r$uc+ solution is prop]ly adju/$4 ,! aldehyde is be/ made z requir$4 ,i employ$ ! ord9>y process z describ$ 9 ,?orpe's ,diction>y ( ,appli$ ,*emi/ry1 by di/ill+ alcohol1 wat]1 sulphuric acid1 & manganese dioxide toge!r4 ,! crude product is mix$ ) a l>ge quantity ( calcium *loride 7dry--n fus$71 & is rectifi$ once4 ,! process is /opp$ :5 ! specific gravity ( ! product rea*es #j4hcb at #fj ,f4 ,! specific gravity ( pure aldehyde is #j4gi ne>ly4 ,! foll[+ is a modification ( ,boettg]'s =mula3- ,solution ,i #a gram ( pure gold is conv]t$ into *loride--got acid free--i4e4 to ! /ate repres5t$ by ,au,cl#c1 & dissolv$ 9 #abj cc4 ( wat]4 ,?is solution is ! equival5t ( "o conta9+ #f4e gra9s ( tri*loride to ! ounce ( wat]4 ,solution ,,ii4 #f grams sodium hydrate4 #ajj grams wat]4 ,solution ,,iii4 #j4b grams glucose 7b\ght z pure74 #ab4f cubic c5timetres #ie p] c5t alcohol4 #ab4f cubic c5timetres wat]4 #b4j cubic c5timetres aldehyde1 sp4 gr4 #j4hcb4 ,to gild glass ^! solutions are us$ 9 ! foll[+ proportions by volume3- #af p>ts ( ,no4 ,i4 #d p>ts ( ,no4 ,,ii4 #j4h p>ts ( ,no4 ,,iii4 ,! glass is fir/ clean$ well ) acid & wa%$ ) wat]3 x is !n r9s$ ) ,solution ,no4 ,,iii4 ,if x is desir$ to gild ! inside ( a glass vessel1 ,solution ,no4 ,,iii4 may be plac$ 9 ! vessel fir/1 & ! walls ( ! vessel r9s$ r\nd c>efully4 ,solutions ,i4 & ,,ii4 are mix$ sep>ately & !n add$ to ,,iii4--aft] ab\t two m9utes ! :ole is well %ak5 up4 ,if x be desir$ to gild a mirror ( glass1 ! glass-plate is susp5d$ face d[nw>ds 9 a di% ( ! mix$ solutions--c>e be+ tak5 to r9se ! glass ) ,solution ,,iii4 fir/4 ,if ! mixture d>k5s 9 f #g' to #aj' 9 diffuse daylight & at #fj;,f4 x w gild well1 & x g5]ally pays to make a few trials 9 a te/ tube to arrive at ?is4 ,if too mu* r$uc+ solution is pres5t ! liquid w get d>k m rapidly1 & vice v]sa4 ,! gild+ w require sev]al h\rs--z mu* z twelve h\rs may be ne$$4 ,! reaction is "o ( great *emical int]e/1 be+ "o ( t class ( reactions :i* is greatly affect$ by capill>ity4 ,?us x occasionally happ5s t :5 ! r$uc+ solution is n 9 ! "r proportion1 gold w be deposit$ at ! surface ( ! liquid 7s z to =m a gilt r+ on ! inside ( a te/ tube71 ! rema9d] ( ! gold go+ d[n z mud4 ,! gold deposit$ is at fir/ transp>5t to transmitt$ light & is deeply blue4 ,i ?\ght ?is might be due to a trace ( copp] or silv]1 b on c>efully purify+ ! gold no *ange ( col\r 0 not$4 ,if ! r$uc+ solution is pres5t 9 slightly great] proportions ?an t giv5 9 ! =mula1 ! gold comes d[n ) a ri*] col\r1 & has a t5d5cy to =m a mat surface & to sep>ate f ! glass4 ,! gold :i* is deposit$ m sl[ly has a less ri* col\r b a bright] surface4 ,! op]ation %\ld be int]rupt$ :5 a suffici5t deposit has be5 obta9$1 because x is f\nd t ! ?ick] ! deposit1 ! m lightly is x held to ! glass surface4 #ge4 ,! ,use ( ! ,diamond-cutt+ ,:eel4 ,a matt] :i* is n v well kn[n outside geological circles is ! manipulation ( ! diamond-cutt+ :eel1 & z ?is is (t5 ( great use 9 ! physical laboratory1 ! foll[+ notes may n be out ( place4 ,i fir/ became acqua9t$ ) ! art 9 connection ) ! necessity :i* arose = me to make galvanomet] mirrors out ( fus$ qu>tz1 & x 0 !n t ,i discov]$ ) surprise h[ difficult x is to obta9 in=mation on ! po9t4 ,i desire to express my indebt$ness to my colleagues1 ,pr(essor ,david & ,mr4 ,smee?1 = ! in/ruction !y h giv5 me4 ,9 :at foll[s ,i propose to describe _! practice r ?an my own1 :i* has be5 ( a make%ift description4 ,i w !re=e select ! process ( cutt+ a slice ( rock = microscopical inve/igation4 #gf4 ,arm+ a ,:eel4 ,fig4 #fc4 ,a conv5i5t :eel is made out ( t9-plate1 i4e4 mild /eel %eet1 ab\t "o-?irtie? ( an in* ?ick & sev5 in*es 9 diamet]4 ,?is :eel mu/ be q flat & true1 z well z r\nd2 too mu* pa9s _c be tak5 9 secur+ ^! qualities4 ,aft] ! :eel is m\nt$1 x is bett] to turn x q true by means ( a wat*-mak]'s grav] or o!r suitable tool4 ,! g5]al design ( a rock-cutt+ ma*9e w be cle> f ! illu/ration 7,fig4 #fc74 ,! :eel be+ set up correctly1 ! next /ep is to arm x ) diamond du/4 ,= ?is purpose x is be=e all ?+s necess>y t real diamond du/ %\ld be obta9$4 ,! be/ plan is to procure a bit ( bort :i* has be5 us$ 9 a diamond drill1 & ^: prop]ties h !re=e be5 te/$ to "s ext5t4 ,?is is gr\nd 9 a diamond mort>--or r hamm]$ 9 "o--& pass$ ?r\gh a sieve hav+ at lea/ #hj ?reads to ! in*4 ,! du/ may be conv5i5tly kept 9 oil4 ,to arm ! :eel1 a little du/ & oil is tak5 on ! f+]1 & laid on r\nd ! p]iph]y ( ! :eel4 ,a bit ( fl9t or agate is !n held firmly aga9/ ! edge ( ! :eel & ! latt] is rotat$ two or ?ree times by h&4 ,! rotation mu/ be q sl[--say "o turn 9 half a m9ute--& ! fl9t mu/ be held firmly & /eadily aga9/ ! :eel4 ,"s op]ators pref] to hamm] ! diamond du/ into ! :eel ) a lump ( fl9t1 or agate1 b !re is a risk ( de=m+ ! :eel 9 ! process4 ,:5 a new :eel is set up1 x may be necess>y to repeat ! above process once e half h\r or s till ! cutt+ is satisfactory1 b :5 once a :eel is well arm$ x w "w = a long "t )\t fur!r att5tion4 #gg4 ,cutt+ a ,section4 ,a :eel #g in*es 9 diamet] may be rotat$ ab\t #ejj times p] m9ute1 & w give good results at t spe$4 ,! "w1 z w be se5 f ! diagram1 is press$ aga9/ ! edge ( ! :eel by a =ce1 :i* 9 ! case quot$ 0 ab\t ! weight ( elev5 ounces4 ,?is 0 di/ribut$ along a cutt+ arc ( ?ree-qu>t]s ( an in*4 ,a conv5i5t cutt+ lubricant is a solution ( ,ca/ile soap 9 wat]1 & ?is mu/ be freely suppli$2 if ! :eel gets dry x is almo/ imm$iately spoil$ ow+ to ! diamond du/ be+ scrap$ (f4 ,9 ! figure ! lubricant is suppli$ by a wick runn+ into ! res]voir4 ,i h us$ bo? clock oil & ord9>y gas-eng9e oil z lubricants1 ) equally satisfactory results4 ,z to ! spe$ ( cutt+1 9 ! exp]im5t quot$ a bit ( r friable gabbro1 measur+ ?ree-qu>t]s ( an in* on ! face by five-eigh?s ( an in* ?ick1 0 cut clean ?r\gh 9 six m9utes1 or by #cjjj turns ( ! :eel4 ,! travel ( ! edge 0 ?us betwe5 #ejjj & #fjjj feet1 or say #ijjj feet1 ne>ly #b miles1 p] in* cut4 ,a good solid rock1 l basalt1 c be cut into slices ( ab\t #c_/cb in* ?ick4 ,a v loose rock is be/ boil$ 9 ,canada balsam1 h>d en\gh to set1 be=e x is put aga9/ ! :eel4 ,in/ead ( a gr9d+ ma*9e a la! may be employ$4 ,! disc is1 ( c\rse1 m\nt$ on ! m&rel1 & ! "w on ! slide-re/4 ,! latt] mu/ be disconnect$ f its fe$ screws1 & a weight arrang$ ov] a pulley s z to keep ! "w press$ aga9/ ! :eel by a con/ant =ce4 ,x may1 p]haps1 occur to ! read] to inquire :e!r any cle>ance 9 ! cut is necess>y4 ,! answ] is t 9 all probability1 & 9 spite ( e c>e1 ! :eel w wobble en\gh to give cle>ance4 ,if x does n1 a little diamond du/ rubb$ into ! side ( ! :eel1 z well z ! edge1 w d all t is requir$4 ,! edge also1 aft] two or ?ree arm+s1 burrs a little1 & ?us provides a cle>ance naturally4 ,x is n unlikely t 9 ! ne> future ! electric furnace w furni% u ) a numb] ( products capable ( replac+ ! diamond z abrad+ ag5ts4 ,! co/ ( ! small am\nt ( diamond du/2 requir$ 9 a laboratory is s small1 h[ev]1 t x2 is d\btful :e!r any appreciable economy w be1 effect$4 #gh4 ,gr9d+ ,rock ,sections1 or ,?9 ,slips ( any ,h>d ,mat]ial4 ,a note on ?is is1 p]haps1 wor? mak+1 = ! same reasons z 7 giv5 = note1 #ge1 :i* x naturally foll[s4 ,j z tr\t-fi%+2 is describ$ by ,mr4 ,francis z ! art ( f9e & f> (f1 ,footnote3 ,9 ! ,badm9ton ,libr>y1 volume on ,fi%+4 section gr9d+ may be call$ ! art ( ,canada balsam cook+1 z foll[s4 ,a section ( rock hav+ be5 cut f ! lump z j describ$1 x becomes2 necess>y to gr9d x d[n = purposes ( microscopical inve/igation4 ,= ?is purpose x is plac$ on a slip ( glass1 & cem5t$ 9 position by ,canada1 balsam4 ,success 9 ! op]ation ( gr9d+ ! m\nt$ section dep5ds almo/ entirely on ! way 9 :i* ! m\nt+ is done1 & ?is 9 its turn dep5ds on ! condition to :i* ! ,canada has be5 br\ght4 ,to illu/rate ! op]ations1 ,i w describe a specific case1 viz4 t ( gr9d+ ! section ( gabbro' above describ$1 = microscopical purposes4 ,"o side ( ! section is probably suffici5tly smoo? & plane f ! op]ation ( ! diamond :eel2 if n1 x mu/ be gr\nd by ! f+] on a slab ( iron or gun-metal ) em]y & wat]1 ! em]y pass+ a sieve ( #hj ?reads to ! in*4 ,! glass base on :i* ! section is to be m\nt$ = gr9d+ is plac$ on a bit ( iron or copp] plate ov] a ,buns5 burn]1 & ?ree or f\r drops ( natural ,canada balsam are plac$ ^u x4 ,! section is plac$ on ! plate to heat at ! same "t4 ,! temp]ature mu/ n rise s high z to cause any visible *ange 9 ! ,canada balsam1 except a slight =mation ( bubbles1 :i* rise to ! surface1 & c be bl[n (f4 ,! heat+ may require to be cont9u$1 say1 up to tw5ty m9utes4 ,! progress ( ! op]ation is te/$ by exam9+ ! balsam z to its visc\s prop]ties4 ,an exce$+ly simple & accurate way ( te/+ is to dip a pair ( ord9>y =ceps 9 ! balsam1 :i* may be /irr$ a little to secure uni=mity4 ,! =ceps are introduc$ ) ! jaws 9 contact1 &1 z soon z )drawn1 ! jaws are all[$ to spr+ ap>t1 ?us draw+ out a balsam ?read4 ,9 a few mom5ts ! ?read is cold1 & if ! =ceps be compress$1 ?is ?read w b5d4 ,! ,canada mu/ be heat$ until x is j 9 su* a /ate t on br++ ! jaws toge!r ! ?read breaks4 ,! =ceps may op5 to ab\t ?ree-qu>t]s ( an in*4 ,if ! ,canada is m visc\s1 s t ! ?read does n break1 ! section :5 cem5t$ by x w mo/ probably slip on ! slide4 ,on ! o!r h&1 if ! balsam is m brittle1 x w crumble away dur+ ! gr9d+4 ,assum+ t ! prop] po9t has be5 rea*$1 ! section is m\nt$ ) ! usual precautions to avoid air bubbles1 i4e4 by dropp+ "o edge on ! balsam fir/4 ,:5 all is cold1 ! surface ( ! section may be gr\nd on an iron plate ) em]y pass+ ! #hj sieve1 till x is ab\t #a_/dj in* ?ick4 ,f ?is po9t x mu/ be r$uc$ on gr\nd glass by fl\rs ( em]y & wat]2 ! r\gh p>ticles ( ! =m] may be wa%$ out = f9e "w4 ,! process ( gr9d+ %\ld n take m ?an half an h\r if ! section is prop]ly cut1 etc4 ,beyond ?is po9t ! all[able ?ickness mu/ dep5d on ! nature ( ! rock2 a good g5]al rule is to get ! section j s ?9 t felsp>s %[ ! yell[ ( ! fir/ ord] 9 a pol>is+1 microscope4 ,! section is !n f9i%$ )1 say1 two m9utes em]y or wat] ( ,ayr-/one du/4 ,x is bett] n to h ! surface too smoo?4 ,to transf] ! section1 ! h>d ,canada r\nd ! sides is scrap$ away1 & ! section itself cov]$ ) "s fre% ,canada f ! bottle4 ,x is !n w>m$ till x w slip (f :5 a p91 or ! invaluable d5ti/'s *isel1 is press$ aga9/ "o side4 ,if ! section be v delicate1 ! cov] slip %\ld be plac$ ov] x be=e x is mov$ to ! prop] slide4 ,! ,canada us$ = m\nt+ is n q s h>d z t employ$ 9 gr9d+1 b x %\ld be h>d :5 cold1 i4e4 n /icky4 ,! art ( prep>+ ,canada balsam appe>s to consi/ 9 heat+ x "u su* conditions z w ensure its be+ expos$ 9 ?9 lay]s4 ,i h wa/$ a good deal ( "t 9 try+ to bake ,canada 9 evaporat+ bas9s1 ) ! inv>iable result t x 0 ei!r ov] or "u-bak$1 & got d>k 9 col\r dur+ ! process4 ,on review+ ! process ( rock section-cutt+ & m\nt+ z j describ$1 ,i _c help ?9k+ t1 if prop]ly sy/ematis$1 x c\ld be made mu* m rapid by ! introduction ( prop] automatic gr9d+ ma*9]y4 ,x also seems n improbable t a prop] ov]haul ( available gums & cem5ts w\ld be f\nd to lead to a cem5t+ mat]ial less tr\blesome ?an ,canada balsam4 #gi4 ,cutt+ ,sections ( ,s(t ,sub/ances4 ,?\gh ?is art is fully treat$ ( 9 books on practical biology1 x is occasionally ( use to ! physici/1 & ! foll[+ note treats ( t "p ( ! subject :i* is n di/9ctly biological4 ,s(t mat]ials1 ( :i* ?9 sections may be requir$1 g5]ally require to be /r5g!n$ be=e !y are cut4 ,= ?is purpose a v>iety ( mat]ials are available4 ,! "o mo/ g5]ally us$ is h>d p>aff94 ,! only po9t requir+ att5tion is ! emb$d+4 ,! mat]ial mu/ be dry4 ,?is is accompli%$ by soak+ 9 absolute alcohol1 i4e4 really absolute alcohol made by %ak+ up rectifi$ _s ) potassium c>bonate1 previ\sly dri$1 & !n dige/+ = a day ) l>ge excess ( quick-lime1 mak+ use ( an inv]t$ cond5s] & f9ally di/ill+ (f ! alcohol )\t all[+ x to come 9 contact ) undri$ air4 ,aft] soak+ = "s "t 9 absolute alcohol1 ! mat]ial may be transf]r$ to oil ( b]gamot1 or oil ( cloves1 or almo/ any ess5tial oil4 ,aft] soak+ 9 ?is long en\gh to all[ ! alcohol to diffuse out1 ! mat]ial may be lift$ into a ba? ( melt$ p>aff9 7melt+ at1 say1 #ea ,c474 ,! process ( soak+ is 9 "s cases made to g m rapidly by exhau/+1 &1 if ! mat]ial w /& x1 by rais+ ! temp]ature ov] #ajj ,c4 ,! soak+ process may require m9utes1 h\rs1 or days1 accord+ to ! size & d5sity ( ! mat]ial2 b a few h\rs are usually suffici5t4 ,:5 cold1 ! sections may be cut 9 any ( ! ord9>y =ms ( microtome4 ,ano!r way ( emb$d+ is to soak 9 collodion1 & !n precipitate ! latt] 9 ! mat]ial & ar\nd x by plung+ into ne>ly absolute alcohol4 ,! collodion yields a h>d] matrix ?an ! p>aff94 ,:atev] =m ( cutt+ ma*9e is employ$1 ! art ( %>p5+ ! knife is ! only "o requir+ any p>ticul> notice4 ,! easie/ way ( obta9+ a knife h>d en\gh to %>p51 is to use a razor ( good quality4 ,if x has to be gr\nd1 x is be/ to d ?is on a f9e ,turkey /one :i* is conv5i5tly re/$ on two bits ( rubb] tub+1 to avoid j>r+ ! blade4 ,_m /ones are slightly crack$1 b on no acc\nt mu/ ! razor be dragg$ across a crack1 or ! edge w suff]4 ,! necess>y & suffici5t condition is t ! razor mu/ be work$ 9 little sweeps ov] ! /one1 & press$ aga9/ ! latt] by little m ?an its own weight1 & ! gr9d+ mu/ be regul>4 ,! edge may be inspect$ "u a microscope1 & x mu/ be p]fectly smoo? & ev5 be=e x w cut sections4 ,a f9i%+ t\* may be giv5 on a lea!r /rap1 b x mu/ be done skilfully1 o!rwise x is bett] omitt$4 ,! necessity = provid+ exceptionally ke5 & %>p edges arose 9 ! manufacture ( phonographs1 :]e ! knife us$ to turn up ! wax cyl9d]s mu/ leave a p]fectly smoo? surface4 ,9 #ahhi ?is 0 be+ accompli%$ on an ivory lap f$ ) a trace ( v f9e diamond du/4 ,i h _h ?is me?od 9 m9d z a possible solution ( ! difficulty ( razor-gr9d+1 b h n tri$ x4 ,i imag9e "o w\ld use a s(t /eel or ivory slip rubb$ ov] ) f9e diamond du/ & oil by means ( an agate4 ,! lap us$ 9 ! phonograph works 0 rotat$ at a high spe$4 #hj4 ,on ! ,production ( ,qu>tz ,?reads4 ,footnote3 ,s9ce ?is 0 writt5 an article on ! same subject by ,mr4 ,boys appe>$ 9 ! ,electrician = #ahif4 ,! in/ructions !re9 giv5 are 9 accordance ) :at ,i _h writt51 & ,i h made no alt]ation 9 ! text4 ,9 #ahhg ! important prop]ties ( fus$ qu>tz 7 discov]$ by ,mr4 ,v]non ,boys 7,philosophical ,magaz9e1 ,june #ahhg1 p4 #dhi1 ,on ! ,production1 ,prop]ties1 & ,"s ,sugge/$ ,uses ( ! ,f9e/ ,?reads74 ,a detail$ /udy ( ! prop]ties ( qu>tz ?reads 0 made by ,mr4 ,boys & communicat$ to ! ,society ( ,arts 9 #ahhi 7,j\rnal ( ! ,society ( ,arts1 #ahhi74 ,an indep5d5t /udy ( ! subject 0 made by ! pres5t writ] 9 #ahhi 7,philosophical ,magaz9e1 ,july #ahij1 ,on ! ,ela/ic ,con/ants ( ,qu>tz ,?reads 74 ,!re is also a pap] 9 ! ,philosophical ,magaz9e = #ahid 7vol4 xxxvii4 p4 #dfc71 by ,mr4 ,boys1 on ,! ,atta*m5t ( ,qu>tz ,fibres4 ,?is pap] also appe>$ 9 ! ,j\rnal ( ! ,physical ,society at ab\t ! same date1 toge!r ) an int]e/+ discussion ( ! matt]4 ,9 ! ,am]ican ,j\rnal1 ,electric ,p[]1 = #ahid1 !re is a s]ies ( articles by ,pr(essor ,ni*ols on ,galvanomet]s1 9 :i* a p>ticul> me?od ( produc+ qu>tz ?reads is recomm5d$4 ,! me?od 0 orig9ally discov]$ by ,mr4 ,boys1 b he seems to h made no use ( x4 ,a hunt ?r\gh ,fr5* & ,g]man lit]ature on ! subject has disclos$ no?+ ( int]e/--no?+ inde$ :i* _c be f\nd 9 ! pap]s m5tion$4 #ha4 ,qu>tz fibres h two great advantages ov] o!r =ms ( susp5sion :5 employ$ = any k9d ( torsion balance1 f an ord9>y m or less a/atic galvanomet] to ! ,cav5di% app>atus4 ,9 ! fir/ place ! actual /r5g? ( ! fibres "u longitud9al /ress is rem>kably high1 rang+ f fifty to sev5ty tons weight p] squ>e in* ( section1 & ev5 m ?an ?is 9 ! case ( v f9e ?reads2 ! second & m important po9t 9 fav\r ( qu>tz dep5ds on ! wide limits )9 :i* cyl9drical ?reads ( ?is mat]ial obey ! simple/ possible law ( torsion1 i4e4 ! law t = a giv5 ?read c>ry+ a giv5 weight at a giv5 temp]ature & hav+ "o end clamp$1 ! twi/ ab\t ! axis ( figure produc$ by a turn+ mom5t appli$ at ! free end is proportional simply to ! mom5t ( ! twi/+ =ces1 & is indep5d5t ( ! previ\s hi/ory ( ! ?read4 ,x is to be not$1 h[ev]1 t ! torsional resili5ce ( qu>tz z te/$ by ! above law is n s p]fect b t our in/rum5tal means all[ u to detect its imp]fections1 & ?us to satisfy ourselves t ?reads made ( qu>tz are n ?+s /&+ ap>t f all o!r mat]ials1 except 9 ! s5se t ! limits )9 :i* !y may be twi/$ )\t deviat+ 9 _! behavi\r f ! law ( /rict proportionality by m ?an "s unassign$ small quantity1 are ph5om5ally wide4 ,a torsion balance--if we except ! case ( c]ta9 spiral spr+s--is almo/ always call$ ^u = in=mation z to ! magnitude ( v small =ces1 & = ?is purpose x is n ess5tial m]ely t "s law ( twi/+ %\ld be exactly obey$1 b also t ! resi/ance to twi/+ ( ! susp5sion %\ld be small4 ,n[1 reg>d$ m]ely z a sub/ance possess+ ela/ic rigidity1 qu>tz is m>k$ly inf]ior to ! majority ( mat]ials1 = x is v /iff inde$2 its utility dep5ds z mu* z any?+ ^u its great /r5g?1 = ?is all[s u to1 use ?reads ( exce$+ f95ess4 ,9 addition to ?is x mu/ be possible1 & moreov] readily possible1 to obta9 ?reads ( uni=m section ov] a suffici5t l5g?1 or ! rate ( twi/ p] unit l5g? ( ! ?read w v>y 9 practice f po9t to po9t1 s t ! limits ( all[able twi/ av]ag$ ov] ! :ole ?read may n be exce$$1 & yet !y may be greatly ov]pass$ at p>ticul> po9ts ( ! ?read4 ,x is int]e/+ to note t 9 ! case ( qu>tz we n only h a means = readily produc+ v uni=m cyl9drical ?reads1 b t ! limits ( all[able rate ( twi/ are s wide t a small dep>ture f uni=mity ( section produces mu* less inconv5i5ce ?an 9 ! case ( any o!r kn[n sub/ance4 #hb4 ,!re are ?ree me?ods g5]ally 9 use = draw+ qu>tz fibres1 all dep5d+ on ! fact t qu>tz :5 fus$ is s visc\s t x may be drawn into ?reads ( great l5g?1 )\t ^! ?reads break+ up into drops1 or inde$ )\t _! %[+ any sign ( do+ s4 ,! surface t5sion ( ! melt$ qu>tz mu/1 h[ev]1 be v consid]able1 z may be se5 by exam9+ ! %ape ( a drop ( ! molt5 mat]ial1 & ?is suffices to impress a rigidly cyl9drical =m ^u ! ?read1 ! great viscosity app>5tly damp+ d[n all oscillation4 ,! fir/ me?od is ! "o orig9ally employ$ by ,mr4 ,boys4 ,a ne$le ( qu>tz is melt$ some:]e 9 its l5g? & is !n drawn out rapidly by a light arr[1 to :i* "o end ( ! ne$le is atta*$1 & :i* is project$ f a k9d ( crossb[4 ,a modification ( ?is me?od1 :i* ! writ] has f\nd ( s]vice :5 v ?ick ?reads are requir$1 is to replace ! b[ & arr[ by a k9d ( catapult4 ,! ?ird me?od1 :i* yields ?reads ( almo/ unmanageable f95ess1 dep5ds on ! exp]im5tal fact t :5 a f9e po9t ( qu>tz is held 9 a high pressure oxyg5 gas bl[-pipe flame1 ! friction ( ! flame gases suffices to ov]come ! t5d5cy ( ! capill>y =ces to produce a sph]ical drop1 & actually causes a f9e ?read to be project$ outw>ds 9 ! direction ( ! flame4 #hc4 ,a prelim9>y op]ation to any me?od is ! production ( a /ick ( fus$ qu>tz4 ,?is is manag$ z foll[s4 ,a rock cry/al or qu>tz pebble is select$ & exam9$4 ,x mu/ be p]fectly :ite1 transp>5t1 & free f dirt4 ,surface impurity c ( c\rse be got rid ( by means ( a gr9d/one4 ,! cry/al is plac$ 9 a p]fectly clean ,/\rbridge clay crucible1 furni%$ ) a cov]1 & heat$ to bright r$ness = ab\t an h\r 9 a clean fire or 9 a ,flet*]'s gas furnace4 ,! cont5ts ( ! crucible are turn$ out :5 suffici5tly cool on to a clean brick or bit ( slate4 ,x w be f\nd t ! cry/al is completely brok5 up & ! fragm5ts mu/ be exam9$ 9 case any ( !m h become contam9at$ by ! crucible1 b ?is w n h happ5$ if ! temp]ature did n rise beyond a bright r$ heat4 ,! heap ( fragm5ts be+ f\nd satisfactory1 ! next ?+ is to fuse "s ( ! pieces toge!r4 ,unless ! prelim9>y heat+ has be5 effici5tly c>ri$ out ?is w prove an annoy+ task1 because a rock cry/al g5]ally conta9s s mu* wat] t x spl9t]s "u ! bl[-pipe 9 a v p]si/5t mann]4 ,!re are two ways ( assembl+ ! fragm5ts4 ,"o is to place two tiles or bricks on edge ab\t ! heap ( qu>tz ly+ ^u a ?ird tile1 s t ! heap occupies ! angul> corn] or nook =m$ by ! tiles 7,fig4 #fd74 ,! oxygas bl[-pipe previ\sly describ$ is adju/$ to give its hotte/ flame1 ! bags be+ weight$ by at lea/ two hundr$weight1 if ( ! size describ$ 7see #ae74 ,! tip ( ! inn] cone ( ! bl[-pipe is br\ght to be> directly ^u "o ( ! fragm5ts1 & if ! op]ation is p]=m$ boldly x w be f\nd t ! surface ( ! fragm5t c be fus$1 & ! fragm5t ?us caus$ to hold toge!r be=e ! l[] side gets hot en\gh to suff] any contam9ation f ! tile or brick4 ,a second fragm5t may be treat$ 9 ! same way1 & !n a ?ird1 & s on4 ,f9ally1 ! fragm5ts may be fus$ toge!r slightly at ! corn]s1 & a /ick may ?us be =m$4 ,( c\rse a good deal ( crack+ & splitt+ ( ! fragm5ts takes place 9 ! process2 ! be/ pieces to op]ate ^u are ^? :i* are well crack$ to beg9 )1 & t 9 su* a way t ! little fragm5ts are int]lock$4 ,an alt]native me?od :i* has "s advantages is to arm a pair ( =ceps ) two /\t plat9um jaws1 say an in* & a half long1 & flatt5$ a little at ! ends4 ,! fragm5ts are held 9 ^! plat9um =ceps & ! bl[-pipe appli$ z be=e4 ,?is me?od works v well 9 add+ to a rod :i* has already be5 p>tly =m$1 b ! jaws require con/ant r5ewals4 ,! fir/ fragm5t :i* is fus$ suffici5tly to coh]e may also be fus$ to a bit ( tobacco pipe1 or h>d glass tube or rod1 & ! qu>tz /ick gradually built up by fus+ fre% pieces on to ! "o already 9 position4 ,fig4 #fd4 ,s9ce ! glass or pipeclay w contam9ate ! qu>tz :i* has be5 fus$ on to x1 x is necess>y to disc>d ! end pieces at ! close ( ! op]ation4 ,a /r+ ( fragm5ts hav+ be5 collect$ & /uck toge!r1 ! next /ep is to fuse !m d[n into a uni=m rod4 ,?is is easily done by hold+ ! /r+ 9 ! bl[-pipe flame & all[+ x to fuse d[n4 ,twi/+ ! fus$ "p has a good effect 9 assi/+ ! op]ation4 ,x is desirable to use a l>ge jet & z p[]ful a flame z c be obta9$ dur+ ?is "p ( ! op]ation4 ,! f9al result %\ld be a rod1 say two or ?ree in*es long & "o-eigh? ( an in* ?ick1 :i* w 9 mo/ cases conta9 a l>ge numb] ( air bubbles4 ,s9ce ! pres5ce ( drawn-out bubbles _c be advantage\s1 x is (t5 desirable to get rid ( !m1 & ?is c conv5i5tly be done at ! pres5t /age4 ,! process at be/ is r t$i\s2 x consi/s 9 draw+ ! qu>tz d[n v f9e be=e an int5se flame1 9 ord] to all[ ! bubbles to get close en\gh to ! surface to bur/4 ,a consid]able loss ( mat]ial inv>iably occurs dur+ ! process2 = :5ev] ! ?9 rod sep>ates into two bits ! process ( flame-draw+ ( ?reads goes on1 & entails a c]ta9 wa/e2 moreov]1 ! qu>tz 9 f9e filam5ts is probably p>tially volatilis$4 ,soon] or lat]1 h[ev]1 a suffici5t l5g? ( bubble-free qu>tz c be obta9$4 ,x mu/ n be suppos$ t x is always necess>y to elim9ate bubbles z p]fectly z is contemplat$ 9 ! =ego+ description ( ! treatm5t1 b = special purposes x may be ess5tial to d s1 & 9 any case ! read]'s att5tion is direct$ to a possible s\rce ( error4 ,x may be m5tion$ 9 connection ) ?is matt] t cry/als ( qu>tz may look p]fectly :ite & cle>1 & yet conta9 impurity4 ,= in/ance1 traces ( sodium are g5]ally pres5t1 & li?ium 0 f\nd 9 l>ge spectroscopic quantity 9 five out ( six samples ( ! pure/ cry/als 9 my laboratory4 ,! pres5ce ( li?ium 9 rock cry/al has also be5 detect$ by ,tegetmei] 7,vi$4 ,ann1 xli4 p4 #ai1 #ahij74 ,aft] "s practice 9 prep>+ rods & free+ !m ( bubbles ! op]ator w notice a di/9ct diff]5ce 9 ! fusibility ( ! samples ( qu>tz he inve/igates1 ?\gh all may appe> equally pure to ! unaid$ eye4 ,x %\ld be m5tion$1 h[ev]1 t high infusibility _c always be tak5 z a te/ ( purity1 = ! mo/ infusible1 or r mo/ visc\s1 sample exam9$ by ! writ] conta9$ m li?ium ?an "s less visc\s samples4 ,fig4 #fe4 ,dur+ ! process ( free+ ! qu>tz f bubbles ! li?ium & sodium w be f\nd to burn away1 or at all ev5ts to disappe>4 ,a rod ( qu>tz1 say ?ree in*es long1 "o-sixte5? ( an in* 9 diamet]1 & free f bubbles = half an in* ( its l5g?1 ev5 :5 exam9$ by a /rong l5s1 is suitable = draw+ into ?reads4 ,! rod is manipulat$ exactly 9 ! mann] describ$ "u glass-bl[+1 & is f9ally drawn d[n at ! bubble free "p into a ne$le1 say #j4jb in* 9 diamet] 7,no4 #be on ! ,birm+ham wire gauge71 & #b in*es long4 ,fig4 #ff4 ,!re is "o peculi>ity ab\t fus$ qu>tz :i* r5d]s its manipulation easi] ?an t ( glass--x is impossible to break fus$ qu>tz1 h[ev] sudd5ly x be ?ru/ into ! bl[-pipe flame4 ,a rod hav+ a diamet] ( ?ree-sixte5?s ( an in*--& p]haps mu* m--may be br\ght "r up to ! tip ( ! inn] cone ( ! oxy-gas flame & held !re-till "o side fuses1 ! o!r be+ comp>atively cool1 )\t ! slighte/ fe> ( precipitat+ a sma%4 ,9 sev5 ye>s' exp]i5ce ,i h nev] se5 a bit ( once fus$ qu>tz brok5 by sudd5 heat+2 :e!r x might be done if suffici5t precautions 7 tak5 ,i d n "k4 ,! reason ( ! =tunate peculi>ity ( qu>tz 9 ?is respect is1 ,i presume1 to be f\nd 9 ! fact t qu>tz once x has be5 fus$ is really a v /rong mat]ial inde$1 & is also probably ! lea/ expansible sub/ance kn[n4 ,f "s exp]im5ts ( ! writ] ^u ! subject1 x may be conclud$ t at ! mo/ qu>tz :i* has be5 fus$ exp&s only ab\t "o-fif? z fa/ z fl9t-glass1 at all ev5ts betwe5 #bj & #gj ,c4 #hd4 ,draw+ ,qu>tz ,?reads4 ,! ?ick end ( ! rod ( qu>tz is held 9 ! f+]s or occasionally 9 a clip4 ,! end ( ! f9e po9t is atta*$ to a /raw arr[ by means ( a little seal+-wax4 ,! arr[ is laid on ! /ock ( a crossb[ 9 ! prop] position = fir+4 ,see ,figs4 #fg & #fh1 :i* practically expla9 !mselves4 ,! ne$le is heat$ by ! bl[-pipe till a m9ute l5g? is 9 a /ate ( uni=m fusion2 ! arr[ is !n let fly1 :5 x draws a ?read out ) x4 ,! arr[ is pref]ably all[$ to /rike a wood5 t>get plac$1 say1 #cj feet away f ! b[1 & a wid? ( black glaz$ calico is laid "u ! l9e ( fire to cat* ! ?read or arr[ if x falls %ort4 ,! g5]al arrangem5ts w be obvi\s f ! figure4 ,! b[ is ( p9e 9 ! case :]e v long ?9 ?reads are requir$1 ?\gh = ord9>y purposes ,i h f\nd a b[ ( lance-wood succe$ q z well4 ,! trigg] ( ! b[ consi/s ( a simple p9 pass+ ?r\gh ! /ock & fa/5$ at its l[] end to a /r+ connect$ ) a bo>d :i* c be depress$ by foot4 ,9 ! figure an ord9>y trigg] is %[n1 b ! p9 does j z well4 ,fig #fg4 ,! arr[ is made out ( ab\t #f in*es ( /raw1 plugg$ up aft by a small plug ( p9e or will[ fa/5$ 9 ) seal+-wax1 & project+ backw>ds "o-eigh? ( an in*4 ,?is projection s]ves a d\ble purpose3 x gives a po9t ( atta*m5t = ! qu>tz ne$le1 & on fir+ ! b[ x =ms a resi/+ anvil on :i* ! /r+ ( ! b[ imp+es4 ,! head ( ! arr[ is =m$ by a l>ge ne$le /uck 9 ) seal+-wax1 & heavy en\gh to br+ ! c5tre ( gravity ( ! arr[ =w>d ( "o-?ird ( its l5g?1 ! condition ( /ability 9 flight4 ,fig4 #fh4 ,x is n necess>y to employ any fea!r+ = ^! arr[s2 ?\gh ,i h occasionally us$ fea!rs or mica to w+ ! %aft no advantage has result$ !refrom4 ,to get f9e ?reads a high velocity is ess5tial4 ,?is is obta9$ by consid]+ 7& act+ ^u7 ! pr9ciples involv$4 ,! b[ may be reg>d$ z a d\bly-tap]+ rod clamp$ at ! middle4 ,aft] deflection x returns t[>ds its equilibrium position at a rate dep5d+ 9 g5]al t]ms on ! ela/ic =ces br\ght into play1 directly1 & on ! effective mom5t ( in]tia ( ! rod1 inv]sely 7see ,rayleigh1 ,s\nd1 vol4 ii4 *ap4 viii47 ,if ! mass ( ! arr[ is negligible comp>$ ) ! b[1 ! rate at :i* ! arr[ moves is practically det]m9$ by t atta9$ by ! end ( ! b[1 :i* is a maximum 9 cross+ its equilibrium position4 ,! ext5t to :i* ! arr[ pr(its by ?is velocity dep5ds on ! way ! b[ is /rung4 ,x w be greate/ :5 ! /r+ is p]p5dicul> to ! b[ :5 pass+ its equilibrium position2 or 9 o!r words1 :5 ! /r+ is inf9itely long4 ,s9ce ! /r+ has mass1 h[ev]1 x is n p]missible to make x too long1 or its weight beg9s to make itself felt1 & a po9t is soon rea*$ at :i* ! geometrical ga9 9 /r+ velocity is comp5sat$ = by ! total loss ( velocity due to ! in]tia ( ! /r+4 ,9 practice x is suffici5t to use a /r+ #aj p] c5t long] ?an ! b[4 ,x is well to use a light fiddle /r+1 s]v$ ) wax$ silk at ! trigg] cat*2 if ?is be omitt$ ! gut gets worn ?r\gh v quickly4 ,9 ord] to decide h[ f> x is p]missible to b5d ! b[1 ! quicke/ way is to make a r\gh exp]im5t on a bit ( ! same plank f :i* ! b[ is to be cut1 & !n to all[ a small factor ( safety4 ,9 ! figure ! b[ is ( lance-wood & is m b5t ?an w\ld be suitable = p9e4 ,! b[ itself is tap]$ f ! middle outw>ds j l any o!r b[4 ,if ?ick ?reads are requir$1 ! above consid]ations are modifi$ by ! fact t qu>tz opposes a consid]able resi/ance to draw+1 & t consequ5tly ! arr[ mu/ n only h a high velocity1 b a fair supply ( en]gy z well2 9 o!r words1 x mu/ be heavy4 ,a ?9 p9e arr[ in/ead ( a /raw g5]ally does v well1 b 9 ?is case ! advantage ( us+ p9e = ! b[ vani%es2 & 9 fact lance-wood does bett]1 ow+ to ! great] displacem5t :i* x w /& )\t break+4 ,?is ( c\rse only means t a great] /ore ( en]gy c be accumulat$ at "o b5d+4 ,i _h occasion to inve/igate :e!r ! unavoidable sp9 ( an arr[ ab\t its axis produces any effect on ! ?read1 & = ?is purpose made arr[s ) in]tia b>s ?ru/ ?r\gh ! head1 i4e4 an arr[ ) a bit ( wire run ?r\gh x1 p]p5dicul> to its l5g?--=m+ a cross 9 fact--! arms ( ! cross be+ weight$ at ! extreme ends by %ot4 ,?is =m ( arr[ has a consid]able mom5t ( in]tia ab\t its long] axis1 & consequ5tly rotates less ?an a m]e /raw1 provid$ t ! c\ples t5d+ to produce rotation are n increas$ by ! cross arm1 or ! velocity too mu* r$uc$4 ,%oot+ "o ( ^! arr[s sl[ly1 ,i c\ld see t x did n rotate1 & :5 fir$ at a high velocity1 x g5]ally arriv$ at ! t>get 7plac$ at v>y+ di/ances front b[7 ) ! arms ne>ly horizontal1 ?us %[+ t x probably did n rotate mu*4 ,i did n succe$ 9 ?is at ! fir/ trial1 by any means4 ,! ?reads got 9 ?is way 7 no bett] ?an ^? made ) a s+le /raw1 :5ce we may conclude v provisionally t ! sp9 ( ! arr[ has only a small effect1 if any1 on ! quality ( ! ?reads4 ,fea!r+ ! arr[1 9 my exp]i5ce1 t5ds1 if any?+ to make x sp9 m2 = "o ?+1 because x is practically impossible to lay ! fea!r+ on /raight4 ,aft] ! arr[ is %ot1 x rema9s to ga!r 9 ! ?read1 & if ! latt] is at all ?91 we h a r tr\blesome job4 ,9 a ?read ?irty or =ty feet long1 ! mo/ uni=m "p g5]ally lies 9 ! middle if ! ?read is ?91 i4e4 ( ! ord] ( a t5-?\s&? ( an in* 9 diamet]4 ,if ! ?read is ?ick ! mo/ uni=m "p may be any:]e4 ,! "p ( ! ?read requir$ is g5]ally be/ isolat$ by pass+ a slip ( pap] "u x at ea* end & cem5t+ ! ?read to ! pap] by means ( a little p>aff9 or s(t wax1 & !n cutt+ (f ! out] portions4 ,"o bit ( pap] may !n be lift$ (f ! calico1 & ! ?read w c>ry ! o!r bit4 ,9 ?is way ! ?read may be tak5 to a black5$ bo>d1 :]e x may be m\nt$ = /ock4 ,by pass+ ! two ends ( ! ?read "u a microscope1 or r by break+ bits (f ! two ends & exam9+ !m toge!r1 x is easy to =m an ,op9ion z to uni=mity4 ,mr4 ,boys has employ$ an optical me?od ( exam9+ ?reads1 b ! writ] has inv>iably f\nd a high-p[] microscope m conv5i5t & capable ( giv+ m exact in=mation z to ! diamet] ( ! ?reads4 ,! beg9n]--or inde$ ! practis$ h&--ne$ n expect to get a ?read ( ! exact dim5sions requir$ at ! fir/ %ot4 ,a little exp]i5ce is necess>y to enable "o to judge ( ! "r ?ickness ( ! ne$le = a ?read ( giv5 diamet]4 ,! ?reads are s easily %ot1 h[ev]1 t a few trials take up v little "t & g5]ally af=d q suffici5t exp]i5ce to enable a ?read ( any requir$ diamet] to be prep>$4 ,x is no use attempt+ to heat an appreciable l5g? ( ne$le2 if ?is be done ! ?read almo/ inv>iably has a ?ick "p ab\t ! middle ( its l5g?44 ,x is suffici5t to fuse at mo/ ab\t "o-tw5tie? ( an in* along ! ne$le be=e fir+ (f ! b[4 ,?is c be done by means ( ! small] oxygas bl[-pipe jet describ$ 9 ! article on bl[-pipes = glass-bl[+1 #ad4 ,! flame mu/ ( c\rse be turn$ d[n s z to be ( a suitable size4 ,a suffici5tly small flame may be got f almo/ any jet4 ,if ! ne$le be n equally heat$ all r\nd1 ! ?read t5ds to be curly2 inde$ by means ( ! catapult1 ?reads may be pull$ :i*1 :5 brok51 t5d to coil up l ! balance-spr+s ( wat*es1 if only c>e be tak5 to h "o side ( ! ne$le mu* hott] ?an ! o!r4 #he4 ,:5 exam9+ bits ( ?reads1 say ?ick] ?an ! two-?\s&? ( an in*1 "u ! microscope x is conv5i5t to use a film ( glyc]9e /a9$ ) "s k9d ( dye1 9 ord] to r5d] ! ?read m %>ply visible4 ,! ?read is m\nt$ b5ea? a cov] slip1 & a drop ( ! /a9$ glyc]9e all[$ to run 94 ,su* a treatm5t gives ! image ( ! ?read a %>ply def9$ edge #c & ! contra/ betwe5 ! :it5ess ( ! ?read & ! col\r ( ! backgr\nd all[s measurem5ts to be made ) great ease4 ,on ! :ole ! easie/ way ( measur+ ! diamet] ( a ?ick ?read is to use a measur+ microscope1 i4e4 "o 9 :i* ! l5s sy/em c be displac$ along a plane b$ by means ( a f9ely cut micromet] screw4 ,! in/rum5ts made by ! ,cambridge ,sci5tific ,in/rum5t ,company d fairly well4 ,direct measurem5ts up to #j4jjja in* are easily made by means ( a microscope provid$ ) a ,zeiss ,a objective1 & r small] diff]5ces ( ?ickness c be made out by x4 ,= ?9 ?reads ! me?od next to be describ$ is m fitt+1 because high] p[]s c be m conv5i5tly us$4 ,9 ?is me?od an ord9>y microscope is employ$ toge!r ) a scale micromet]1 & ei!r an eyepiece micromet]1 or a cam]a & subsidi>y scale4 ,! eyepiece micromet] is ! m conv5i5t4 ,if a cam]a be employ$1 i4e4 su* an "o z is suppli$ by ,zeiss1 x is a/oni%+ h[ ! accuracy ( obs]vation may be increas$ by att5d+ c>efully to ! illum9ation ( bo? ! subsidi>y scale & ( ! ?read4 ,! two images %\ld be z f> z possible ( equal brightness1 & = ?is purpose x w be f\nd requisite to employ small scre5s4 ,! detail ( mak+ a measurem5t by means ( ! micromet] eyepiece is v simple4 ,! ?read is arrang$ on ! /age s z to po9t t[>ds ! obs]v]1 & ! app>5t diamet] is read (f on ! eyepiece scale4 ,9 ord] to calibrate ! latt] x is only necess>y to replace ! ?read by ! /age micromet]1 & to obs]ve ! numb] ( /age micromet] divisions occupy+ ! space 9 ! eyepiece micromet] =m]ly occupi$ by ! ?read4 ,x is ess5tial t bo? ?read & /age micromet] %\ld occupy ! same position 9 ! field1 = errors due to unequal di/ortion may o!rwise become ( importance4 ,= ?is reason x is be/ to utilise ! c5tre ( ! field only4 ,! same rem>k applies to measurem5ts by means ( ! cam]a1 :]e ! image ( ! ?read is project$ aga9/ ! reflect$ image ( ! subsidi>y scale laid alongside ! microscope4 ,9 ?is case ! value ( ! subsidi>y scale divisions mu/ be obta9$ f ! divisions ( ! /age micromet]1 co9cid+ z ne>ly z possible ) ! position occupi$ by ! ?read4 ,be=e comm5c+ a measurem5t ! scre5s are mov$ ab\t till bo? images appe> equally bright4 ,?reads up to ab\t "o tw5ty-?\s&? ( an in* 9 diamet] may be suffici5tly well measur$ by means ( a ,zeiss #d c5timetre apo*romatic object-glass & an eyepiece ,no4 #f ) sixte5 c5timetre tube l5g?4 ,footnote3 ,! objective c]ta9ly _h #d cm4 m>k$ on x1 b ! focal l5g? appe>$ to be ab\t ,i4#e mm4 only4 #hf4 ,draw+ ,?reads by ! ,catapult4 ,! b[-&-arr[ me?od fails :5 ?reads ( a great] diamet] ?an ab\t #j4jjae in* are requir$--at lea/ if any reasonable uni=mity be dem&$1 & no radical *ange 9 ! b[ & arr[ be c>ri$ out4 ,?us 9 ! writ]'s laboratory a ?read ( ab\t ?is diamet]1 )9 #a_/ajjjj ( an in*-#ac in*es long & free f air bubbles--0 requir$4 ,a =tnight's "w by a mo/ skilful op]ator only result$ 9 ! production ( two l5g?s satisfy+ ! conditions4 ,! greate/ loss ( "t occurs 9 ! exam9ation ( ! ?read by means ( ! microscope4 ,?reads = galvanomet] susp5sions are conv5i5tly f #j4jjja to #j4jjjd in* 9 diamet]1 & are mu* m easily made & got uni=m ?an ?ick] ?reads1 to ! production ( :i* ! catapult me?od applies4 ,a ref]5ce to ! diagram w make ! con/ruction ( ! in/rum5t q cle>4 ,! mov+ end ( ! qu>tz is atta*$ to a small boxwood slid] work+ on a tubul> gird] or betwe5 wires4 ,! qu>tz is secur$ 9 position by clamps %[n at ,a & ,b1 & motion is imp>t$ to ! slid] by a /ret*$ piece ( catapult ela/ic 7,c74 ,an easy means ( regulat+ ! pull ( ! ela/ic is to hold x back by a loop ( /r+ ^: l5g? c be v>i$ by twi/+ x r\nd a p94 ,fig4 #fi4 ,footnote3 ,= great] cle>ness ( draw+1 ! tube c>ry+ ! slid] is %[n some:at high] above ! base ?an is conv5i5t 9 practice2 & ! slide itself is %[n too ?9 9 ! direction ( ! hole ?r\gh x4 ,s9ce x is n p]missible to all[ ! slid] to reb\nd at ! end ( its j\rney1 "s su* arrangem5t ( breaks z is %[n mu/ be adopt$4 ,9 ! diagram ! bottom ( ! slid] runs on to a brass spr+ betwe5 ! gird] & ! base ( ! appliance1 & s gets jamm$2 ! spiral spr+ acts m]ely z an additional gu>d4 ,! diagram does n %[ ! l[] spr+ v cle>ly2 x is a m]e /rip ly+ 9 ! groove4 ,a rod ( qu>tz1 ) a ne$le at "o end1 is prep>$ z be=e & secur$ 9 ! clamps4 ,dur+ ! op]ation ( fa/5+ d[n ! clamps1 !re is "s dang] ( break+ ! ne$le1 & consequ5tly x is advisable to s(t5 ! latt] be=e & :ile adju/+ ! second clamp4 ,! process ( draw+ a ?read by ?is me?od is exactly simil> to ! op]ation already describ$ 9 connection ) ! arr[ me?od4 ,?\gh %ort ?ick ?reads =m ! product g5]ally obta9$ f ! catapult1 x mu/ n be suppos$ t ?9 ?reads _c be obta9$ 9 ?is way4 ,if a %ort l5g? ( a v f9e ne$le be heat$1 x w be f\nd to yield ?reads q f9e en\gh = ord9>y susp5sion purposes1 b naturally n s uni=m z ^? obta9$ f ! #dj-;foot l5g?s obta9able by ! b[-&-arr[ me?od4 ,x is easy to make spiral qu>tz spr+s resembl+ wat* balance-spr+s by means ( ! catapult4 ,all t is necess>y is to see t ! qu>tz is r unequally heat$ be=e ! %ot is fir$4 ,9 ! future x is by no means impossible t su* spr+s may h a real value1 = ! rigidity ( qu>tz is kn[n to increase z temp]ature rises4 ,h5ce x is probable t ! spr+s w\ld become /iff] z temp]ature rises1 ev5 ?\gh !y "w *iefly by b5d+1 & little or n at all by twi/+4 ,z ?is is ! k9d ( temp]ature v>iation requir$ to comp5sate an uncomp5sat$ wat* balance :eel1 x may turn out to h "s value4 #hg4 ,draw+ ,?reads by ! ,flame alone4 ,a /ick ( qu>tz is drawn d[n to a f9e po9t1 & ! tip ( ?is po9t is held 9 ! bl[-pipe flame 9 ! position %[n 9 ,fig4 #gj4 ,fig4 #gj4 ,! friction ( ! flame gases is f\nd to be suffici5t to c>ry =w>d ! fus$ qu>tz & to draw x into ?reads 9 spite ( ! influ5ce ( ! capill>y =ces4 ,if a %eet ( pap] be susp5d$ at a di/ance ( two or ?ree feet 9 front ( ! bl[-pipe flame1 x w be f\nd to be cov]$ ) f9e ?reads tangl$ toge!r into a cobwebby mass4 ,z ?is me?od is an exce$+ly simple "o ( obta9+ ?reads1 ,i h endeav\r$ to r$uce x to a sy/ematic op]ation4 ,a %eet ( c>dbo>d1 ab\t two feet squ>e1 is pa9t$ dead black & susp5d$ horizontally1 pa9t$ side d[nw>ds 7,fig4 #gj1 ,a71 at a height ( ab\t two feet above ! bl[-pipe flame4 ,! latt] is adju/$ s z to po9t almo/ v]tically upw>ds & t[>ds ! c5tre ( ! c>dbo>d4 ,a few half-in* p9s are ?ru/ ?r\gh ! c>d f ! upp] surface & pu%$ home2 ab\t "o doz5 p9s scatt]$ ov] ! surface w be suffici5t4 ,_! object is to prev5t ! ?reads be+ c>ri$ away r\nd ! edge ( ! scre54 ,! flame f ! jet describ$ s (t5 is f$ f gas bags weight$ to ab\t eighty p\nds p] squ>e foot ( 7"o7 surface1 i4e4 #d-;foot bags require f ?ree to f\r hundr$weight to give an advantage\s pressure4 ,footnote3 ,! result+ ?reads 7 really too f9e = conv5i5t manipulation1 s t unless extremely f9e ?reads are requir$ x w be bett] to r$uce ! pressure ( ! gases consid]ably4 ,two /icks ( qu>tz are introduc$ & caus$ to meet j 9 front ( ! inn] cone--! hotte/ "p ( ! flame4 ,!y are !n drawn ap>t s z to =m a f9e neck1 :i* s(t5s & is b5t 9 ! direction ( motion ( ! flame gases4 ,:5 fusion is complete ! neck sep>ates into two p>ts1 & a ?read is drawn f ea* ( !m4 ,by alt]nately lightly t\*+ ! rods toge!r1 & draw+ !m ap>t1 q a mass ( ?reads may be obta9$ 9 two or ?ree m9utes1 :5 ! process %\ld be /opp$4 ,if too _m ?reads get entangl$ 9 ! p9s1 "o gives "o's self ! unnecess>y tr\ble ( sep>at+ !m4 ,on tak+ d[n ! c>d x w be f\nd t ! ?reads h be5 caught by ! p9s2 b ! c>d n[ be+ laid black side upw>ds1 ! =m] easily slip (f ! po9ts4 ,?reads at lea/ a foot long1 & p]haps va/ly long]1 may be obta9$ by ?is me?od1 & are extraord9>ily f9e4 ,:5 ,i fir/ read ,pr(essor ,ni*ols' /atem5t 7,electric ,p[]1 #ahid7 z to ! value ( ^! fibres = galvanomet] purposes1 ,i 0 r sceptical on ! gr\nd t ! ?reads w\ld t5d to get anneal$ by be+ drawn gradually1 in/ead ( sudd5ly1 f a place ( int5se heat to regions ( l[] temp]ature4 ,n[ anneal+ ?reads by a ,buns5 makes !m rott54 ,! ?reads be+ imm]s$ 9 ! hot flame gases c\ld only cool at ! same rate z ! gas1 & x 0 n--& is n--cle> to me t anneal+ ( ! ?reads c be avoid$4 ,on ! o!r h&1 x may be possible t a ?read cool$ sl[ly f ! fir/ does n suff] 9 ! same way z a cold ?read w\ld d :5 anneal$ 9 a ,buns5 flame4 ,aga9 ! velocity ( ! gases is beyond d\bt exce$+ly high1 s t ! anneal+1 ev5 suppos+ x to be delet]i\s1 might n be c>ri$ v f>4 ,?reads drawn by ?is me?od & measur$ dry1 i4e4 by m\nt+ !m on a slide )\t ! addition ( any liquid1 turn$ out to h a diamet] ( ab\t #a_/bjjjj ( an in*4 ,i d n ?9k ,i c\ld manage to m\nt su* f9e ?reads )\t v special tr\ble4 ,all ! ?reads ly+ on ! bo>d1 h[ev]1 7 f\nd 9 reality to consi/ ( ?ree or f\r sep>ate ?reads1 & !re is no reason :y sev]al ?reads %\ld n be m\nt$ 9 p>allel1 provid$1 ( c\rse1 t !y are equally /ret*$ & t\*+ ea* o!r4 ,equality ( t5sion 9 ! m\nt+ c\ld be secur$ by mak+ "o atta*m5t good1 !n cem5t+ ! o!r atta*m5t to ! o!r end ( ! ?reads1 & draw+ ! two atta*m5ts slightly ap>t at ! mom5t ! cem5t comm5ces to set4 ,?is me?od may turn out to be v valuable1 =1 s f> z ,i c see1 ! c>ry+ p[] w\ld be increas$ )\t an increase ( torsional /iffness ( any?+ l s high an ord] z w\ld be ! case 7 "o ?read only employ$4 ,on ! o!r h&1 ! law ( torsion c\ld h>dly be q s simple1 at all ev5ts1 to ! second ord] ( approximations4 #hh4 ,prop]ties ( ,?reads4 ,a l>ge numb] ( exp]im5ts on ! num]ical values ( ! ela/ic con/ants ( qu>tz ?reads h be5 made by ,mr4 ,boys & 8 /ud5ts1 & by ! writ]4 ,z ! me?ods employ$ 7 q di/9ct & ! results :olly indep5d5t1 & yet 9 good agreem5t ) ea* o!r1 a r\nd$ av]age may be accept$ ) consid]able confid5ce4 ,,t5acity ,,( ,,qu>tz ,,fibres 7,,boys74 ,diamet] ( ,?read4 ,t5acity 9 ,tons' ,weight p] ,squ>e ,in* ( ,section4 ,t5acity 9 ,dynes p] ,squ>e ,c5timetre4 ,in*es ,c5timetres #j4jjjfi #j4jjage #ea4g #h ,x #aji #j4jjjai #j4jjjdh #gd4e #aa4e ,x #aji ,r\nd$ mean ( ,boys' & ,?relfall's results3 ,"y's ,modulus at #bj ,c1 #e4f ,x #ajaa ,c4,g4,s4 ,modulus ( ,simple ,rigidity at #bj ,c1 #b4fe ,x #ajaa ,c4,g4,s4 ,modulus ( ,incompressibility1 #a4d ,x #ajaa ,c4,g4,s4 ,modulus ( ,torsion1 #c4g ,x #ajaa ,c4,g4,s4 ,approximate coeffici5t ( l9e> expansion ( qu>tz p] degree betwe5 #hj ,c4 & #cj ,c4 is #j4jjjjjag 7,?relfall loc4 cit474 ,?is mu/ be reg>d$ ) "s suspicion1 z ! data 7 n concordant4 ,!re is no d\bt1 h[ev]1 ab\t ! extreme inexpansibility ( qu>tz4 ,temp]ature coeffici5t ( modulus ( torsional rigidity p] degree c5tigrade1 #bb to #ih ,c1 #j4jjjacc ,ditto1 absolute simple rigidity1 #j4jjjabh 7,?relfall74 ,limit ( all[able rate ( twi/ 9 r\nd numb]s is1 "o-?ird turn p] c5timetre1 9 a fibre #j4ja cm4 diamet]4 ,! limit+ rate is probably r\ghly inv]sely z ! diamet]4 ,att5tion mu/ be call$ to ! rapid increase 9 ! torsional rigidity ( ^! ?reads z ! temp]ature rises4 ,a qu>tz spiral spr+-balance w be appreciably /rong] 9 hot wea!r4 #hi4 ,9 ! majority ( in/ances 9 :i* qu>tz ?reads are appli$ 9 ! laboratory1 x is desirable to keep ! coeffici5t ( torsion z small z possible1 & h5ce ?reads are us$ z f9e z possible4 ,x is conv5i5t to rememb] t a ?read #j4jjad cm4 or #j4jjjg in* 9 diamet] breaks ) a weight ( ab\t t5 grammes1 & may conv5i5tly be employ$ to c>ry1 say1 five grammes4 ,) ?reads ?ree times f9] ! break+ /r5g? p] unit area increases1 say1 #ej p] c5t4 ,9 ord9>y practice--galvanometric "w = in/ance--:]e x is desirable to use a ?read z f9e & %ort z possible to su/a9 a weight up to1 say1 half a gramme1 x w be f\nd t fibres five c5timetres long or ov] give no tr\ble ?r\gh defect ( ela/ic prop]ties4 ,a factor ( safety ( two is a fair all[ance :5 load+ ?reads4 ,no difficulty w be exp]i5c$ 9 m\nt+ ?reads hav+ a diamet] ( #j4jjjb in* or ov]4 ,) f9] ?reads x is necess>y to employ v d>k backgr\nds 7,mr4 ,boys uses ! d>kness ( a slightly op5$ draw]71 or ! ?reads _c be suffici5tly well se54 ,9 ! case ( in/rum5ts 9 :i* ?reads rema9 highly twi/$ = long p]iods ( "t1 ! above rule z to ! safe limit ( twi/ does n all[ ( a suffici5t m>g92 x is only applicable to galvanometric & simil> purposes4 ,! cause ( ! increase 9 t5acity z ! diamet] dim9i%es is at pres5t unkn[n4 ,x is due nei!r to an effect ( anneal+ 7anneal$ ?reads are rott571 nor is x a sk9 effect1 nor is x due to ! cool+ ( ! ?read "u high] capill>y pressure4 ,x is1 h[ev]1 possible t x may be associat$ ) "s k9d ( p]man5t set tak5 by ! fibres dur+ ! /age ( passage f ! liquid to ! solid /ate4 #ij4 ,on ! ,atta*m5t ( ,qu>tz ,fibres4 ,= _m purposes x is suffici5t to cem5t ! fibres 9 position by means ( ord9>y yell[ %ellac1 b :]e v great accuracy is aim$ at1 ! %ellac 7be+ itself imp]fectly ela/ic & expos$ to %e>+ /ress7 imposes its imp]fections on ! :ole sy/em4 ,?is s\rce ( error c be got ov] by sold]+ ! ?reads 9 position4 ,attempts 7 made by ! writ] 9 ?is direction1 ) fair success1 9 #ahhi1 b z ,mr4 ,boys has c>ri$ ! art to a high degree ( p]fection1 ,i w suppress ! description ( my own me?od & describe 8 9 pref]5ce4 ,x has1 ( c\rse1 be5 frequ5tly repeat$ 9 my laboratory4 ,9 _m cases1 h[ev]1 if n 9 all1 x may be replac$ by ,m>got sold]+1 z already describ$1 a note on ! application ( :i* to ?is purpose w foll[4 ,a ?read ( ! prop] diamet] hav+ be5 select$1 x is cut to ! "r l5g?4 ,) f9e ?reads ?is is n always a p]fectly easy matt]4 ,! be/ way is = ! op]ator to /ation himself fac+ a good light1 n sunlight1 :i* is too tir+ to ! eye1 b bright diffus$ light4 ,! ?read w be furni%$ ) bits ( pap] /uck on ) p>aff9 at bo? ends1 z already describ$4 ,a r\gh sket* ( ! app>atus--or1 at all ev5ts1 two l9es %[+ ! exact l5g? :i* ! free "p ( ! ?read mu/ h--are m>k$ on a smoo? bo>d1 & ?is is support$ ) its plane v]tical4 ,! ?read is held aga9/ ! bo>d1 & ! upp] piece ( pap] is /uck lightly to ! bo>d ) a trace ( s(t wax1 s t ! l[] edge ( ! pap] is at any desir$ height above ! upp] m>k4 ,?is di/ance is measur$1 & =ms ! l5g? ( ?read all[$ to ov]lap ! support4 ,a second bit ( pap] is atta*$ bel[ ! l[] m>k1 a m>g9 = ! atta*m5t ( ! l[] end be+ measur$ & left z be=e4 ,! ?read w be mo/ easily se5 if ! bo>d is pa9t$ a dead black4 ,if x is desir$ to atta* ! ?read to its supports m]ely by %ellac1 ?is is practically all t ne$s to be done4 ,! supports %\ld resemble l>ge p9s4 ,! upp] support w be a brass wire 9 mo/ cases1 & w require to be fil$ away z %[n 9 ! sket* 7,fig4 #ga74 ,x is !n coat$ ) %ellac by heat+ & rubb+ ^u ! %ellac4 ,z previ\sly not$1 ! %ellac mu/ n be ov]heat$4 ,! ?read is cut (f bel[ ! l[] slip ( pap]1 & ! upp] support be+ conv5i5tly laid 9 a horizontal position on ano!r dead-black surface1 ! ?read is c>ri$ to x & laid z design$ aga9/ ! %ellac1 :i* is n[ cold4 ,:5 ! ?read is 9 place1 a sold]+ iron is put aga9/ ! brass wire1 & ! %ellac gradually melt$ till x closes ov] ! ?read4 ,fig4 #ga4 ,! iron is !n )drawn & ! ?read pull$ away f ! po9t = "o-tw5tie? ( an in* or less4 ,?is ensures t ! ?read makes prop] contact ) ! cem5t1 & also t x is free f k9ks2 ( c\rse1 x mu/ leave ! cem5t 9 ! prop] direction4 ,a simil> process is next c>ri$ out ) respect to ! l[] atta*m5t1 & ! ends ( ! ?read are neatly trimm$ (f4 ,bo? ends ( ! ?read be+ secur$1 ! next /ep is to transf] ! upp] support to a clip /&1 ! susp5d$ p>ts be+ held by h&1 s t ! weight comes on ! ?read v gradually4 ,9 ?is way x w be easily se5 :e!r ! ?read is b5t :]e x ent]s ! %ellac1 & %\ld ?is be ! case1 a hot iron mu/ be br\ght up to ! %ellac & ! error rectifi$4 ,:5 bo? ! support & ! susp5d$ p>ts are br\ght ne>ly to ! requir$ be>+1 ! hot iron is held = a mom5t close up to ea* atta*m5t1 ! h& be+ held close bel[ b n t\*+ ! susp5d$ p>ts1 & bo? atta*m5ts are all[$ to /raight5 !mselves out naturally4 ,^! details may appe> tiresome1 & s !y are :5 writt5 out at l5g?1 b ! "t occupi$ 9 c>ry+ !m out is v %ort1 & qu>tz ?reads break easily1 unless ! pull ^u !m is accurately 9 ! direction ( _! l5g? at all po9ts4 ,9 ! ev5t ( its be+ decid$ to atta* ! ?read by sold]+1 ! process is r m exp5sive 9 "t1 b n o!rwise m tr\blesome4 ,fig4 #gb4 ,fig4 #gc4 ,! ?read be+ cut z be=e to ! prop] l5g?1 little bits ( alum9ium foil are sme>$ all ov] ) melt$ %ellac & susp5d$ f ! ?read replac+ ! pap] slips be=e describ$4 ,x is important t no p>aff9 %\ld be all[$ to t\* ! ?read any:]e ne> a po9t int5d$ to be sold]$4 ,! ?read is hung up f a clip /& by "o ( ! bits ( foil1 & ! l[] end is wa%$ by dipp+ x into /rong nitric acid = a mom5t & !nce into wat]4 ,! object ( sme>+ ! foils all ov] ) %ellac is to prev5t !m be+ act$ ^u by ! acid4 ,! ?reads are n v easily wa%$ acid free1 b ! process may be assi/$ by means ( a f9e camel's-hair p5cil4 ,"s silv]+ solution made z describ$ 7 #fe7 is put into a te/ tube2 ! ?read1 aft] r9s+ ) di/ill$ wat]1 is l[]$ into ! solution s f> z is requir$1 & is all[$ to receive a coat+ ( silv]4 ,x has be5 obs]v$ t ! coat+ ( silv] mu/ n be too ?ick--n suffici5tly ?ick to be opaque4 ,a wat* may be kept on ! process by imm]s+ a m9ute /rip ( mica alongside ! ?read4 ,! silv]$ ?read is r9s$ ) di/ill$ wat] & all[$ to dry4 ,mean:ile ! o!r end ( ! ?read may be silv]$4 ,:5 bo? ends are silv]$ ! process ( copp]+ by electro deposit is comm5c$4 ,a te/ tube is p>tially fill$ ) a t5 p] c5t solution ( sulphate ( copp]1 & sev]al copp] wires are dipp$ into x to =m an anode4 ,! ?read is l[]$ c>efully into ! solution s z n to introduce air bubbles1 & ! silv]$ "p is all[$ to project f> en\gh above ! surface ( ! solution to come 9 contact ) a f9e copp] wire4 ,! circuit is clos$ ?r\gh a ,leclan* cell & a resi/ance box4 ,x is z well to beg9 ) a fair resi/ance1 say #ajj ohms out 9 ! box1 & ! progress ( ! deposit is wat*$ by means ( a l[-p[] microscope set up 9 front ( ! ?read4 ,if ! copp] appe>s to come d[n 9 a granul> =m1 ! resi/ance is too small & mu/ be increas$2 if no headway appe>s to be made1 ! resi/ance mu/ be dim9i%$4 ,z soon z a fair coat ( copp] has come d[n1 i4e4 :5 ! diamet] ( ! ?read is ab\t d\bl$1 ! process is int]rupt$4 ,! ?read is )drawn1 wa%$1 dipp$ 9 a solution ( *loride ( z9c1 & c>efully t9n$ by dragg+ x ov] a small clean drop ( sold] on a sold]+ bit4 ,dur+ ?is "p ( ! process ! %ellac is apt to get melt$ if ! iron is held too close1 s t x is advisable to beg9 by mak+ ! ?read some:at ov] long4 ,! end ( ! ?read mu/ only be trimm$ (f at ! conclusion ( ! op]ation1 i4e4 aft] ! ?read is sold]$ up4 ,! ?read is atta*$ to ! previ\sly t9n$ supports mu* 9 ! same way z has be5 describ$ "u ! head ( %ellac atta*m5ts4 ,x does n v mu* matt] :e!r bo? ends are copp]$ be=e "o is sold]$ up or n4 ,at ! conclusion ( ! :ole process ! sup]flu\s copp] & silv] are dissolv$ (f by a little hot /rong nitric acid appli$ on a glass hair p5cil4 ,?is is be/ done by hold+ ! ?read horizontally ) ! assi/ance ( clip /&s4 ,if ! ?read is too delicate to be> bru%+1 ! nitric acid may be appli$ by p\r+ out a big drop into a bit ( plat9um foil & hold+ ?is bel[ ! ?read s z to t\* x lightly4 ,! dissolv+ ( ! copp] & silv] is1 ( c\rse1 foll[$ by copi\s wa%+ ) hot wat]4 ,?is process is m labori\s ?an might be imag9$1 b x may be %ort5$ by heat+ ! plat9um foil support+ ! wat] 7,fig4 #gd74 ,fig4 #gd ,! wa%+ "p ( ! process is1 9 ! op9ion ( ! writ]1 ! mo/ difficult "p ( ! :ole bus9ess1 & x requires to be v ?or\gh1 or ! ?read w end by draw+ out ( ! sold]4 ,9 _m cases x is bett] to try to d )\t any application ( nitric acid at all1 b1 ( c\rse1 ?is involves silv]+ & copp]+ to exact di/ances f ! ends ( ! ?read--at all ev5ts1 9 app>atus :]e ! effective l5g? ( ! ?read is n>r[ly prescrib$4 ,x is important n to leave ! active p>ts ( ! ?read appreciably silv]$1 = ! sake ( avoid+ z]o *anges due to ! imp]fect ela/icity ( ! silv]4 ,9 ?is sold]+ process ord9>y t9man's sold] may be employ$2 x mu/ be appli$ v free f du/ or oxide4 #ia4 ,o!r ,modes ( sold]+ ,qu>tz4 ,?ick rods ( qu>tz may be treat$ = atta*m5t by sold] 9 ! same way z glass 0 treat$ by ,pr(essor ,kundt to get a f\ndation = 8 electrolytically deposit$ prisms4 ,footnote3 ,see ,app5dix at end ( book4 ,! application ( a drop ( a /rong solution ( plat9um tetra*loride to ! rod w1 on dry+1 give rise to a film ( ! dry salt1 & ?is may be r$uc$ 9 ! lum9\s gas flame4 ,dur+ ! process1 h[ev]1 ! qu>tz is apt to get rott51 especially if ! temp]ature has be5 any?+ approa*+ a full r$ heat4 ,! result+ plat9um deposit adh]es v /rongly to ! qu>tz1 & may be sold]$ to z be=e4 ,?is me?od has be5 employ$ by ! writ] ) success s9ce #ahhg1 & may ev5 be ext5d$ to ?ick ?reads4 ,x 0 also f\nd t fusible metal ei!r /uck to or contract$ ^u clean qu>tz s z to make a firm jo9t4 ,9 ! light ( ,m4 ,m>got's rese>*es 7already describ$71 x occurr$ to me t p]haps my exp]i5ce 0 only a special case ( ! ph5om5a ( adhesion inve/igat$ ) s mu* success by ,m4 ,m>got4 ,i !re=e tri$ :e!r ! alloy ( t9 & z9c us$ = sold]+ alum9ium w\ld /ick to qu>tz1 & in/antly f\nd t ?is 0 inde$ ! case4 ,adhesion betwe5 ! alloy & p]fectly clean qu>tz takes place almo/ )\t rubb+4 ,a rod ( qu>tz ?us t9n$ c be sold]$ up to any?+ to :i* sold] w /ick1 at once4 ,on apply+ ! me?od to ?ick qu>tz ?reads1 success 0 in/antane\s 7! ?reads 7 "s pres]v$ = ord9>y galvanomet] susp5sions72 b :5 ! me?od 0 appli$ to v f9e ?reads1 great difficulty 9 t9n+ ! ?reads 0 exp]i5c$4 ,! op]ation is be/ p]=m$ by hav+ ! alloy on ! end ( an alum9ium sold]+ bit1 & tak+ c>e t x is p]fectly free f oxide be=e ! ?read is drawn across x4 ,!re 0 no difficulty 9 sold]+ a ?read t9n$ 9 ?is mann] to a copp] wire ) t9man's sold]1 & ! jo9t appe>$ p]fect1 ! ?read break+ f9ally at ab\t an in* away f ! jo9t4 ,i all[ ,mr4 ,boys' me?od to /& z ,i h writt5 x1 simply because ,i h n _h "t z yet to make ?or\gh te/s ( ! durability ( ,m>got jo9ts on ! f9e/ ?reads2 b ,i h practically no d\bt z to its p]fect applicability1 provid$ always t ! sold] c be got clean en\gh :5 melt$ on ! bit4 ,v f9e ?reads w require to be /ret*$ be=e t9n+1 9 ord] to enable !m to break ?r\gh ! capill>y b>ri] ( ! surface ( ! melt$ sold]4 #ib4 ,sold]+4 ,x is almo/ unfair to ! arts ( ! glass-bl[] or optician to describe !m side by side ) ! humble trade ( sold]+4 ,nev]!less1 no accompli%m5t ( a me*anical k9d is s s]viceable to ! physici/ z h&9ess ) ! sold]+ bit2 &1 z a rule1 !re is no o!r ex]cise 9 :i* ! av]age /ud5t %[s su* lam5table incapacity4 ,! foll[+ rem>ks on ! subject are !re=e address$ to p]sons presumably q ignorant ( ! way 9 :i* sold]+ is c>ri$ out1 & d n pr(ess to be m ?an ( ! mo/ elem5t>y "*4 ,= laboratory purposes ?ree k9ds ( sold] are 9 g5]al suffici5t4 ,"o is ! ord9>y t9man's sold] compos$ ( lead & t94 ,! second is spelt]1 or s(t fusible brass1 & ! ?ird is an alloy ( silv] & brass call$ silv] sold]4 ,t9man's sold] is us$ = mo/ purposes :]e high temp]atures are n requir$1 or :]e ! app>atus is int5d$ to be tempor>y4 ,! spelt]1 :i* is really only f9ely granulat$ fusible brass1 is us$ = braz+ iron jo9ts4 ,! silv] sold] is conv5i5t = mo/ purposes :]e p]man5cy is requir$1 & is especially suit$ to ! jo9+ ( small objects4 #ic4 ,s(t t9man's sold] is made by melt+ toge!r two p>ts ( gra9 t9 & "o ( s(t lead--! exact proportions are n ( consequ5ce--b1 on ! o!r h&1 ! pur] ! con/itu5ts ! bett] ! sold]4 ,)9 c]ta9 limits1 ! great] ! proportion ( t9 ! clean] & m fusible is ! sold]4 ,x is usually wor? :ile to prep>e ! sold] 9 ! laboratory1 = 9 ?is way a uni=m & dep5dable product is assur$4 ,good s(t lead is melt$ 9 an iron ladle & skimm$2 ! temp]ature is all[$ to rise v little above ! melt+-po9t4 ,! t9 is !n add$ little by little1 ! alloy /irr$ vigor\sly & skimm$1 & /icks ( sold] conv5i5tly ca/ by sweep+ ! ladle ov] a clean iron plate1 s z to p\r out a ?9 /ream ( sold]4 ,if ! sold] be prop]ly made x w h a mat & bright mottl$ surface1 & w crackle :5 held up to ! e> & b5t4 ,p]haps ! *ief precaution necess>y 9 mak+ sold] is to exclude z9c4 ,! pres5ce ( a v small p]c5tage ( ?is metal entirely spoils ! sold] = t9man's "w by prev5t+ its runn+ or fl[+ smoo?ly "u ! sold]+ bit4 ,fig4 #ge4 ,fig4 #gf4 ,fig4 #gg4 #id4 ,prep>+ a ,sold]+ ,bit4 ,! w$ge-%ap$ edge ( "o ( ! =ms ( bit %[n 9 ! sket* is fil$ to %ape & ! bit heat$ 9 a fire or on a gas heat]4 ,a bit ( r\gh s&/one1 or ev5 a clean s(t brick1 or a bit ( t9 plate hav+ "s s& spr9kl$ ov] x1 is plac$ 9 a conv5i5t position & spr9kl$ ) res94 ,z soon z ! bit is hot en\gh to melt sold] x is )drawn & a few drops ( sold] melt$ on to ! brick or its equival5t4 ,! iron or bit is !n rubb$ to & fro ov] ! sold] & res9 till ! =m] adh]es to & t9s ! copp] head4 ,x w be f\nd advisable to t9 e side ( ! po9t ( ! bit & to c>ry ! t9n+ back at lea/ half an in* f ! edge4 ,if ! sold] ob/9ately refuses to adh]e1 ! cause is to be s\ght 9 ! oxidation ( ! copp]1 or ( ! sold]1 or bo?--9 ei!r case ! result ( too high a temp]ature or too prolong$ heat+4 ,! simple rem$y is to get ! iron hot1 & !n to dress x ) an old file1 s z to expose a bright surface1 :i* is in/antly pass$ ov] ! res9 z a means ( pres]v+ x f oxidation4 ,if ! process above describ$ be n[ c>ri$ out1 x w be f\nd t ! difficulty disappe>s4 ,be=e us+ ! iron1 wipe (f any soot or coke or burn$ res9 by means ( an old rag4 ,an iron t9n$ 9 ?is way is mu* to be pref]r$ to "o t9n$ by means ( *loride ( z9c4 ,a %ort] & m usual me?od is c>ri$ out z foll[s3 ,! solution ( *loride ( z9c is prep>$ by add+ bits ( z9c to "s comm]cial hydro*loric acid dilut$ ) a little 7say #be p] c5t7 ( wat]4 ,! acid may conv5i5tly be plac$ 9 a small glaz$ :ite j> 7a jam pot does excell5tly71 & ?is %\ld only be fill$ to ab\t "o-qu>t] ( its capacity4 ,an excess ( z9c may be add$4 ,x may be fancy1 b ,i pref] a sold]+ solution made 9 ?is way to a solution ( *loride ( z9c b\ght z a *emical product4 ,! j> is g5]ally m\nt$ on a heavy lead5 base1 s z to avoid any dang] ( its gett+ knock$ ov]1 = no?+ is s na/y or bad = tools z a b5* on :i* ?is noxi\s liquid has be5 upset 7,fig4 #gh74 ,fig4 #gh4 ,to t9 a sold]+ bit1 a little ( ! fluid is dipp$ out ( ! j> on to a bit ( t9 plate b5t up at ! edges--a few drops is suffici5t--& ! iron is heat$ & rubb$ ab\t 9 ! liquid ) a drop ( sold]4 ,if ! iron is any?+ l clean x w t9 at once & exhibit a v bright surface1 b q dirty copp] may be t9n$ by dipp+ x = a mom5t 9 ! liquid 9 ! pot & !n work+ x ab\t ov] ! sold]4 ,an iron s t9n$ rema9s cov]$ ) *loride ( z9c1 & ?is mu/ be c>efully wip$ (f if x is int5d$ to use ! iron ) a res9 or tall[ flux 9 lead sold]+4 ,"o disadvantage ( ?is process is t ! copp] bit soon gets eat5 into holes & requires to be dress$ up afre%4 ,on ! o!r h&1 an iron s t9n$ always pres5ts a nice clean sold] surface until ! next "t x is heat$1 :5 x g5]ally becomes v dirty & requires to be c>efully wip$ be=e us+4 ,9 my exp]i5ce also an iron s t9n$ is m easily spoil$ z to ! /ate ( its surface1 det9n$1 9 fact1 by ov]heat+ ?an :5 ! t9n+ is c>ri$ out by res9 & friction4 ,:5 ?is happ5s1 ! %orte/ way out ( ! difficulty is ! application ( ! old file s z to obta9 a p]fectly fre% surface4 ,no "o :o kn[s 8 bus9ess ev] uses an iron t is n p]fectly clean & well t9n$4 ,! iron may be clean$ f "t to "t by heat+ x r$ hot & qu5*+ x 9 wat] to get rid ( ! oxide1 :i* scales (f 9 ! process4 #ie4 ,s(t ,sold]+4 ,9 ! laboratory ! *ief application ( ! process is to copp] sold]+ dur+ ! con/ruction ( electrical app>atus & to z9c sold]+ = g5]al purposes4 ,9 n9ety-n9e cases out ( e hundr$ :]e difficulties occur _! orig9 is to be trac$ to dirt4 ,!re seems to be "s inexplicable k9k 9 ! human m9d :i* r5d]s x call\s to repeat$ pro(s ( ! necessity = clean+ surfaces :i* x is int5d$ to sold]4 ,! slighte/ trace ( album9\s or gelat9\s matt] or %ellac w prev5t sold] adh]+ to mo/ metals & ! same rem>k applies 9 a measure to ! pres5ce ( oxides1 al?\gh ^! may be remov$ by *loride ( z9c or prev5t$ f =m+ by res9 or tall[4 ,a t\* ) an ord9>ily dirty h&--,i ref] to a sold]]'s h&--w (t5 soil "w suffici5tly to make ! adh]5ce ( sold] difficult4 ,! fluxes mo/ g5]ally employ$ are tall[ = lead1 res9 or ,v5ice turp5t9e = copp]1 *loride ( z9c = any?+ except lead1 :i* nev] requires x4 ,! latt] flux has ! prop]ty 7also possess$ by borax at a r$ heat7 ( dissolv+ any traces ( oxide :i* may be =m$1 z well z act+ z a protect+ lay] to ! metal4 ,we may n[ turn to ! consid]ation ( a simple case ( sold]+1 say ! jo9+ ( two copp] wires4 ,! wires are fir/ clean$ ei!r by dipp+ 9 a ba? ( sulphuric & nitric acids--a ?+ no laboratory %\ld be )\t--or by any suitable me*anical means4 ,! clean$ wires are !n twi/$ toge!r--!re is a regulation way ( do+ ?is1 b x pres5ts no advantage 9 laboratory practice--& ! jo9t is spr9kl$ ov] ) res91 or pa9t$ ) a solution ( res9 9 alcohol4 ,! iron1 be+ heat$ & float$ ) sold]1 is held aga9/ ! jo9t1 ! latt] be+ support$ on a brick1 & ! sold] is all[$ to sweat into ! jo9t4 ,en\gh sold] mu/ be pres5t to p5etrate "r ?r\gh ! jo9t4 ,no?+ is ga9$ by rubb+ viol5tly ) ! iron4 ,if ! copp] is clean x w t91 & if x is dirty x won't1 & !re ! matt] ends4 ,beg9n]s g5]ally use too small or too cold a bit1 & produce a ragg$1 dirty jo9t 9 consequ5ce4 ,if ! sav+ ( "t be an object1 ! jo9t may be twi/$ toge!r on ord9>ily dirty oxidis$ wires & heat$ to1 say1 #bjj ,c4 ,x is !n pa9t$ ) *loride ( z9c & sold]$ ) ! bit4 ,!re is a diff]5ce ( op9ion z to ! relative m]its ( *loride ( z9c & ( res9 z a flux 9 sold]+ copp]4 ,?us ! /&+ ,g]man practice is1 or 01 to employ ! =m] flux 9 e case = sold]+ electric light wires1 :ile 9 ,engl& ! cu/om us$ to be to specify t sold]+ %\ld be done by res91 & ?is cu/om may /ill prevail2 x l+]s 9 ,au/ralia at all ev5ts4 ,h[ev]1 x is agre$ on all h&s t :5 *loride ( z9c is us$ x mu/ be c>efully wa%$ (f4 ,i h kn[n ( an electrical eng9e] insi/+ on 8 workm5 lick+ jo9ts ) _! tongues to ensure ! total removal ( *loride ( z9c2 x has a horrible ta/e2 & ,i h occasionally pursu$ ! same plan myself :5 ! sold]+ ( f9e wires 0 9 "q4 ,9 any case1 x is v c]ta9 t *loride ( z9c left 9 a jo9t w ru9 x soon] or lat] by loos5+ ! contact betwe5 copp] & sold]4 ,v (t5 x is requisite to sold] toge!r two ext5sive flat surfaces--= in/ance1 9 *uck+ c]ta9 k9ds ( brass "w4 ,! surfaces to be sold]$ mu/ be c>efully t9n$1 mo/ conv5i5tly by ! help ( ! bl[-pipe & *loride ( z9c4 ,aft] t9n+1 ! surfaces are laid toge!r & heat$ s z to sweat !m toge!r2 ! phrase1 ?\gh inelegant1 is expressive4 #if4 ,sold]+ ,t9 ,plate4 ,if ! plate be new & clean1 a little res9 or its solution 9 alcohol is all t is necess>y z a flux4 ,if ! t9 plate is ru/y ! ru/ mu/ be remov$ & ! clean iron1 or r mild /eel1 surface expos$4 ,! use ( *loride ( z9c is practically ess5tial 9 ?is case4 ,t9 plate is (t5 spott$ ) ru/ long be=e x becomes ru/y z a :ole1 :51 ( c\rse1 x may be reg>d$ z worn out1 & su* ru/ spots are mo/ conv5i5tly remov$ by means ( ! plumb]'s %ave-hook4 ,! %ave-hook is m]ely a peculi>ly %ap$ h>d /eel scrap+ knife on a h&le 7,fig4 #gi74 ,fig4 #gi ,) t9 plate ! sold]+ ( long jo9ts is (t5 necess>y4 ,! plate mu/ be tempor>ily held 9 position ei!r by b9d+ ) iron wire1 fa/5+ by clamps1 or hold+ by an assi/ant4 ,! flux is appli$ & ! iron run sl[ly along ! jo9t4 ,en\gh sold] is us$ to completely float ! tip ( ! iron4 ,by arrang+ ! jo9t s t x slopes d[nw>d slightly1 & comm5c+ at ! upp] end1 ! sold] may be caus$ to fl[ aft] ! iron1 & w leave a jo9t ) ! m9imum p]missible am\nt ( sold] 9 x4 ,by regulat+ ! slope1 heat ( iron1 etc1 any desir$ quantity ( sold] may be run into ! jo9t4 #ig4 ,sold]+ ,z9c4 ,z9c alloys ) s(t sold] v easily1 & by s do+ entirely spoils x1 mak+1 x crumbly1 dirty1 & prev5t+ x runn+4 ,consequ5tly1 9 sold]+ up z9c great c>e mu/ be tak5 to prev5t ! sold] becom+ appreciably contam9at$ by ! z9c4 ,to ?is end ! z9c surfaces are clean$ by means ( a little hydro*loric acid1 :i* is pa9t$ on in/ead ( *loride ( z9c4 ,pl5ty ( sold] is melt$ on to ! "w1 & is drawn along ov] ! jo9t by a s+le sl[ motion ( ! sold]+ bit4 ,! iron mu/ be j hot en\gh to make ! sold] fl[ freely1 & x mu/ nev] be rubb$ viol5tly on ! z9c or all[$ to l+] 9 "o spot2 ! result ( ! latt] action w be to melt a hole ?r\gh ! z9c1 ow+ to ! t5d5cy ( ?is metal to =m an easily fusible alloy ) ! sold]4 ,! art ( sold]+ z9c is a v useful "o 9 ! laboratory4 ,! majority ( physici/s appe> to ov]look ! advantages ( z9c consid]$ z a mat]ial = app>atus con/ruction4 ,x is light1 fairly /rong1 *eap1 easily fusible1 & yet h>d & ela/ic :5 cold4 ,x may be work$ z easily z lead at a temp]ature (1 say1 #aej to #bjj ,c1 & slightly bel[ ! melt+-po9t 7#dbc ,c47 x is brittle & may p[d]$4 ,! prop]ty ( s(t5+ at a mod]ate temp]ature is invaluable z a means ( flatt5+ z9c plate or %ap+ x 9 any way4 ,dur+ ! "w x may be held by means ( an old clo?4 ,z9c %eet :i* has be5 heat$ betwe5 iron plates & flatt5$ by pressure reta9s its flatness v fairly well aft] cool+4 #ih4 ,sold]+ o!r ,metals4 ,iron4 ,! iron mu/ be fil$ clean & !n bru%$ ) *loride ( z9c solution4 ,"s p add a little sat ammoniac to ! *loride ( z9c1 b ! improvem5t ?us made is practically inappreciable4 ,if ! iron is clean x t9s q easily1 & ! process ( sold]+ x is p]fectly easy & requires no special comm5t4 ,brass4 ,! same me?od z describ$ = iron succe$s p]fectly4 ,! brass1 if n exce$+ly dirty1 may be clean$ by heat+ to ! temp]ature at :i* sold] melts 7bel[ #bjj ,c471 & pa9t+ x ov] ) *loride ( z9c1 or dipp+ x 9 ! liquor4 ,if n[ ! brass be heat$ aga9 9 ! bl[-pipe flame1 x w be f\nd to t9 p]fectly well :5 rubb$ ov] ) sold]4 ,g]man ,silv]1 ,plat9oid1 ,silv]1 & ,plat9um are treat$ l iron4 ,) reg>d to silv] & plat9um ! same precautions z recomm5d$ 9 ! case ( z9c mu/ be obs]v$1 = bo? ^! metals =m fusible alloys ) sold]4 ,gold :5 pure requires no flux4 ,/&>d gold1 :i* conta9s copp]1 sold]s bett] ) a little *loride ( z9c4 ,lead mu/ be p>$ absolutely clean & !n sold]$ quickly ) a hot iron1 us+ tall[ z a flux4 ,s9ce sold] if ov] hot w adh]e to lead almo/ any:]e1 plumb]s are 9 ! habit ( specially soil+ ^? p>ts to :i* x is n int5d$ t sold] %all adh]e4 ,! soil+ pa9t consi/s ( v ?9 glue1 call$ size1 mix$ ) lampblack2 on an em]g5cy a raw potato may be cut 9 half1 & ! "w to be soil$ may be rubb$ ov] ) ! cut surface ( ! potato4 ,h>d ,c>bon or gas coke may be sold]$ aft] coat+ ) copp] by an electrolytic process1 z w be describ$4 #ii4 ,braz+4 ,sold]+ at a r$ heat by means ( spelt] is call$ braz+4 ,spelt] is s(t brass1 & is g5]ally made f z9c "o "p1 copp] "o "p2 an alloy easily granulat$ at a r$ heat2 x is pur*as$ 9 ! granul> =m4 ,! art ( braz+ is appli$ to metals :i* w )/& a r$ heat1 & ! jo9ts s sold]$ h ! /r5g? ( brass4 ,! pieces to be jo9t$ by ?is me?od mu/ be c>efully clean$ & held 9 _! prop] relative positions by means ( iron wire4 ,x is g5]ally necess>y to s(t5 iron wire z pur*as$ by heat+ x r$ hot & all[+ x to cool 9 ! air2 if ?is is n done ! wire is usually too h>d to be employ$ satisfactorily = b9d+4 ,v ?9 wire--i4e4 above ,no4 #bj on ! ,birm+ham wire gauge--does n d1 = x gets burn$ ?r\gh1 & p]haps all[s ! "w to fall ap>t at a critical mom5t4 ,! "w be+ securely fa/5$1 ! next /ep is to cov] ! clean$ p>ts ) flux 9 ord] to prev5t oxidation4 ,= ?is purpose glass borax is employ$4 ,glass borax is simply ord9>y borax :i* has be5 fus$ = ! purpose ( gett+ rid ( wat] ( cry/allisation4 ,! glass borax is r$uc$ to p[d] 9 an iron mort>1 = x is v h>d1 & is !n made up into a cream ) a little wat]4 ,?is cream is pa9t$ on to ! p>ts ( ! "w :i* are de/9$ to receive ! sold]4 ,! next /ep is to prep>e ! spelt]1 & ?is is easily done by mix+ x ) ! cream1 tak+ c>e to /ir ?or\ghly ) a flatt5$ iron wire till ea* p>ticle ( spelt] is p]fectly cov]$ ) ! borax4 ,! mixture %\ld n be too wet to behave z a granul> mass1 & may !n be lift$ on to ! "w by means ( ! iron spatula4 ,c>e mu/ be tak5 to place ! spelt] on ^? p>ts only :i* are int5d$ to receive x1 & :5 ?is is done1 ! jo9t may be lightly p[d]$ ov] ) ! dry borax1 & w !n be ready = heat+4 ,if ! object is ( consid]able size x is mo/ conv5i5tly heat$ on ! =ge2 if small ! bl[pipe is m conv5i5t4 ,9 ! latt] case1 place ! "w on a firebrick1 & arrange two o!r bricks on edge ab\t x1 s t x lies m or less 9 a corn]4 ,a few bits ( coke may also be plac$ on & ab\t ! "w to increase ! temp]ature by _! combu/ion1 & to conc5trate ! flame & prev5t radiation4 ,! temp]ature is gradually rais$ to a bright r$ heat1 :5 ! spelt] w be obs]v$ to fuse or run1 z x is te*nically said to d4 ,if ! clean+ & di/ribution ( flux has be5 successful1 ! spelt] w run along ! jo9t v freely1 & ! "w %\ld be tapp$ g5tly to make sure t ! spelt] has really run into ! jo9t4 ,! heat+ may be int]rupt$ :5 ! spelt] is obs]v$ to h melt$ into a cont9u\s mass4 ,z soon z ! "w has fall5 bel[ a r$ heat x may be plung$ into wat]1 a process :i* has ! effect ( crack+ (f ! glass-l lay] ( borax4 ,!re is1 h[ev]1 "s risk ( caus+ ! "w to buckle by ?is viol5t treatm5t1 :i* mu/ ( c\rse be modifi$ s z to suit ! circum/ances ( ! case4 ,if ! jo9t is 9 su* a position t ! borax _c be fil$ (f1 a v conv5i5t in/rum5t = its removal by scrap+ is ! wat*mak]'s grav]1 a squ>e rod ( h>d /eel gr\nd to a bevell$ po9t 7,fig4 #hj74 ,fig4 #hj4 ,sev]al precautions require to be m5tion$4 ,9 ! fir/ place1 spelt] is m]ely r s(t brass1 & consequ5tly x (t5 _c be fus$ )\t endang]+ ! re/ ( ! "w4 ,a good protection is a lay] ( fireclay laid ^u ! m delicate p>ts1 su* = in/ance z any screw$ "p4 ,gun-metal & tap-metal d n l5d !mselves to braz+ s readily z iron or yell[ brass1 & are usually m conv5i5tly treat$ by means ( silv] sold]4 ,spelt] t5ds to run v freely :5 x melts1 & if ! brass surface 9 ! neighb\rhood ( ! jo9t is at all clean1 may run :]e x is n want$4 ,( c\rse "s control may be ex]cis$ by soil+ ) fireclay or us+ an oxidis+ flame2 b ! erratic behavi\r ( spelt] 9 ?is respect is ! greate/ drawback to its use 9 app>atus con/ruction4 ,! secret ( success 9 braz+ lies 9 prop]ly clean+ up ! "w to beg9 )1 & 9 dispos+ ! borax s z to prev5t subsequ5t oxidation4 #ajj4 ,silv] ,sold]+4 ,?is process resembles t la/ describ$1 b in/ead ( spelt] an alloy ( silv]1 copp]1 & z9c is employ$4 ,! sold]1 z prep>$ by jewell]s to meet special cases1 v>ies a good deal 9 composition1 b = ! laboratory ! usual proportions are3 ,= s(t silv] sold] ,f9e silv] #b p>ts ,brass wire #a "p ,= h>d silv] sold] ,/]l+ silv] #c p>ts ,brass wire #a "p ,! latt] is1 p]haps1 g5]ally ! m conv5i5t4 ,silv] sold]s may1 ( c\rse1 be pur*as$ at wat*mak]s' supply %ops1 & z ?us obta9$1 are g5]ally 9 ?9 %eet4 ,?is is snipp$ f9e ) a pair ( %e>s prep>atory to use4 ,z odds & ends ( silv] 7f old anodes & silv] residues7 g5]ally accumulate 9 ! laboratory1 x is (t5 m conv5i5t to make ! sold] "o's self4 ,9 ?is case x mu/ be rememb]$ 9 mak+ h>d sold] by ! second receipt t /&>d silv] conta9s ab\t "o-twelf? ( its weight ( copp]--exactly #ah p>ts copp] to #bbj silv]4 ,! silv] is fir/ melt$ 9 a plumbago crucible 9 a small furnace toge!r ) a little borax2 if any copp] is requir$ ?is is !n add$1 & f9ally ! brass is introduc$4 ,:5 fusion is complete1 ! cont5ts ( ! crucible are p\r$ into any suitable m\ld4 ,! quicke/ & mo/ conv5i5t way ( prep>+ ! alloy = use is to conv]t x into fil+s ) ! assi/ance ( a co>se file1 or by mill+ x1 if a mill+ ma*9e is available4 ,equal volumes ( fil+s & p[d]$ glass borax are made into a ?9 pa/e ) wat]1 & appli$ 9 an exactly simil> mann] to t describ$ "u ! head ( braz+4 ,9 fact all ! processes !re describ$ may be appli$ equally to ! case "u discussion1 ! sub/itution ( silv] = spelt] be+ ! only v>iation4 ,! silv] sold] is m manageable ?an spelt]1 & does n t5d to run wild ov] ! "w3 a prop]ty :i* makes x mu* m conv5i5t bo? = delicate jo9ts & 9 cases :]e x is desir$ to re/rict ! sold] to a s+le po9t or l9e4 ,small objects are almo/ inv>iably sold]$ ) silv] sold]1 & are held by =ceps or on *>coal 9 ! po9t$ flame ( an ord9>y bl[-pipe4 #aja4 ,on ! ,con/ruction ( ,electrical ,app>atus3 ,insulators4 ,x is n int5d$ to deal 9 any way ) ! design ( special examples ( electrical app>atus1 b m]ely to describe a r miscellane\s set ( mat]ials & processes con/antly requir$ 9 its con/ruction4 ,x is n kn[n :e!r !re is su* a ?+ z a p]fect insulator1 ev5 if we presuppose ideal circum/ances4 ,mat]ials z !y exi/ mu/ be reg>d$ m]ely z ( high specific resi/ance1 t is if we all[ ourselves to use su* a t]m 9 connection ) sub/ances1 conduction ?r\gh :i* is nei!r indep5d5t ( electromotive =ce p] unit l5g?1 nor ( previ\s hi/ory4 ,ev5 ! be/ ( ^! sub/ances g5]ally get coat$ ) a lay] ( moi/ure :5 expos$ to ! air1 & ?is z a rule conducts fairly well4 ,v pure cry/all9e sulphur & fus$ qu>tz suff] f ?is defect less ?an any o!r sub/ances ) :i* ! writ] is acqua9t$1 b ev5 ) !m ! surface conductivity soon gr[s to su* an ext5t z totally to mask ! int]nal conduction4 ,x is propos$ to give a brief acc\nt ( ! prop]ties ( "s insulat+ sub/ances & _! application 9 electrical con/ruction1 & at ! same "t to indicate ! appliances & me?ods requisite = work+ !m4 ,) reg>d to ! specific resi/ances :i* w be quot$1 ! numb]s mu/ n be tak5 to mean too mu*1 p>tly = ! reason already giv54 ,x is also 9 g5]al d\btful :e!r suffici5t c>e has be5 tak5 to di/+ui% ! body f ! surface conductivity1 & consequ5tly num]ical e/imates are to be reg>d$ ) suspicion4 ,! "q ( sampl+ also arises1 = x mu/ be rememb]$ t a *ange 9 composition am\nt+ to1 say1 #a_/ajjjj p] c5t may be accompani$ by a million-fold *ange 9 specific resi/ance4 #ajb4 ,sulphur4 ,?is elem5t exi/s 9 sev]al allotropic =ms1 :i* h v diff]5t electric prop]ties4 ,aft] melt+ at ab\t #abe ,c1 & anneal+ at #aaj = sev]al h\rs1 ! soluble cry/all9e modification is =m$4 ,aft] keep+ = "s days--especially if expos$ to light--! cry/als lose _! optical prop]ties1 b rema9 ( ! same melt+-po9t1 & are p]fectly soluble 9 c>bon bisulphide4 ,! *ange is accompani$ by a *ange 9 col\r1 or r 9 brightness1 z ! transp>5cy *anges4 ,! specific resi/ance ( sulphur 9 ?is condition is above #ajbh ,c4,g4,s4,e4,m4 units1 or #ajac megohms p] cubic c5timetre = an electric int5sity ( say #ab1jjj volts p] c5timetre4 ,?is is at ord9>y temp]atures4 ,at #ge ,c4 ! specific resi/ance falls to ab\t #ajbe "u simil> conditions z to voltage4 ,9 all cases ! conductivity appe>s to increase ) ! electric int5sity1 or at all ev5ts ) an increase 9 voltage1 ! ?ickness ( ! lay] ( sulphur rema9+ ! same4 ,! specific inductive capacity is #c4afb at ord9>y temp]atures1 & increases v slightly ) rise ( temp]ature4 ,footnote3 ,m>* #ahig4--;,x is n[ ! op9ion ( ! writ] t ?\gh ! specific inductive capacity ( a giv5 sample ( a solid elem5t is p]fectly def9ite1 yet x is v difficult to obta9 two samples hav+ exactly ! same value = ?is con/ant1 ev5 9 ! case ( a mat]ial s well def9$ z sulphur4 ,! total residual *>ge1 aft] t5 m9utes' *>g+ ) an int5sity ( #ab1jjj volts p] c5timetre1 is n m ?an #d p>ts 9 #aj1jjj ( ! orig9al *>ge4 ,9 mak+ ?is measurem5t ! dis*>ge occupi$ a fraction ( a second4 ,! electric /r5g? = a homog5e\s plate ( cry/all9e sulphur is n less ?an #cc1jjj volts p] c5timetre1 & probably a good deal m4 ,if ! sulphur is contam9at$ ) up to #c p] c5t ( ! amorph\s v>iety1 z is ! case if x is cool$ fairly quickly f a temp]ature ( #agj ,c4 or ov]1 ! specific resi/ance falls to f #ajbe to #ajbf at ord9>y temp]atures2 & ! specific inductive capacity increases up to #c4ge1 accord+ to ! am\nt ( insoluble sulphur pres5t4 ,! residual *>ge "u circum/ances simil> to ^? describ$ above1 b ) an int5sity ( ab\t #djjj volts p] c5timetre is1 say1 #b p] c5t ( ! initial *>ge4 ,s f> z ! writ] is aw>e sulphur is ! only solid non-conductor :i* c be easily obta9$ 9 a condition ( approximate purity & 9 samples suffici5tly exactly comp>able ) "o ano!r2 x is ! only "o1 !re=e1 t repays any detail ( description4 ,v pure sulphur c be b\ght by ! ton if necess>y f ! ,unit$ ,alkali ,company ( ,newca/le-on-,tyne4 ,x is recov]$ f sulphur wa/e by ! ,*ance process1 :i* consi/s 9 conv]t+ ! sulphur into hydrog5 sulphide1 & burn+ ! latt] ) insuffici5t air = complete combu/ion4 ,! sulphur is ?r[n out ( comb9ation1 & =ms a cry/all9e mass on ! walls & floor ( ! *amb]4 ,! sulphur :i* comes into ! m>ket consi/s ( ?is mass brok5 up into conv5i5t fragm5ts4 ,9 ord] to purify x suffici5tly = use z an insulator1 ! sulphur may be melt$ at a temp]ature ( #abj to #adj ,c1 & filt]$ ?r\gh a plug ( glass wool 9 a z9c funnel2 z ?us prep>$ x is an excell5t insulator4 ,to obta9 ! results m5tion$ 9 ! table x is1 h[ev]1 necess>y to conduct a fur!r purification 7*iefly f wat]7 by di/illation 9 a glass retort4 ,! sulphur ?us obta9$ may be ca/ ( any desir$ =m 9 z9c m\lds1 ! ca/+s & m\lds be+ imm$iately remov$ to an anneal+ ov5 at a temp]ature ( f #ajj to #aaj ,c1 :]e !y are left = sev]al h\rs4 ,if ! sulphur is kept melt$ = "s "t at #abe ,c4 ! anneal+ is n s important4 ,! ca/+s may be remov$ f ! m\ld by slightly heat+ ! latt]1 b _m breakages result4 ,insulators made on ?is plan are mu* less affect$ by ! cond5sation ( moi/ure f ! air ?an any?+ except fus$ qu>tz4 ,!y are1 h[ev]1 v weak me*anically1 & apt to crack by exposure to su* *anges ( temp]ature z g on f day to day4 ,x is cle>1 h[ev]1 t 9 spite ( ?is _! magnific5t electrical prop]ties fit !m = _m important uses4 ,if ! sulphur be cool$ rapidly f #agj ,c4 or ov]1 a mixture ( ! cry/all9e & amorph\s v>ieties ( sulphur is obta9$4 ,?is mixture is v mu* /rong] & t\gh] ?an ! purely cry/all9e sub/ance1 & may be work$ ) ord9>y h>dwood tools into fairly p]man5t plates1 rods1 etc4 ,%eets ( pure ?ick filt] pap] may also be dipp$ into sulphur at #agj ,c1 at :i* temp]ature air & moi/ure are mo/ly expell$1 & su* %eets %[ a v consid]able insulat+ p[]4 ,! sulphur does n p5etrate ! pap]1 :i* !re=e m]ely =ms a nucleus4 ,cakes ( ! cry/all9e or mix$ v>ieties may be made by gr9d+ up "s purifi$ sulphur1 moi/5+ x ) r$i/ill$ c>bon bisulphide1 or tolu5e1 or ev5 b5z5e 7,c#f;,h#f71 & press+ x 9 a suitable m\ld "u ! hydraulic press4 ,! plates ?us =m$ are por\s1 b are spl5did insulators1 especially if made f ! cry/all9e v>iety ( sulphur1 & !y appe> to keep _! %ape v well1 & d n crack ) ord9>y temp]ature *anges4 ,! metals :i* resi/ ! action ( sulphur be/ are gold & alum9ium2 :ile plat9um & z9c are practically unact$ ^u at temp]atures bel[ a r$ heat--9 ! =m] case1--& bel[ ! boil+-po9t ( sulphur 9 ! latt]4 ,a v conv5i5t te/ ( ! purity ( sulphur is ! col\r assum$ by x :5 sudd5ly cool$ f ! temp]ature at :i* x is visc\s4 ,q pure sulphur rema9s ( a pale lemon yell[ "u ?is treatm5t1 b ! slighte/ trace ( impurity1 su* z arises f du/ conta9+ organic matt]1 /a9s ! sulphur1 & r5d]s x d>k] 9 col\r4 #ajc4 ,fus$ ,qu>tz4 ,?is is on ! :ole ! mo/ reliable & mo/ p]fect insulator = g5]al purposes4 ,no exact num]ical data h be5 obta9$1 b ! resi/ivity mu/ c]ta9ly be ( ! same ord] z t ( pure sulphur at its be/4 ,! influ5ce ( ! moi/ure ( ! air also rea*es its m9imum 9 ! case ( qu>tz1 z 0 orig9ally obs]v$ by ,boys4 ,z yet1 h[ev]1 ! mat]ial c only be obta9$ 9 ! =m ( rods or ?reads4 ,= mo/ purposes rods ( ab\t "o-eigh? ( an in* 9 diamet] are ! mo/ conv5i5t4 ,^! rods may be us$ z insulat+ supports1 & succe$ p]fectly ev5 if !y int]pose less ?an an in* ( _! l5g? to electrical conduction4 ,! sket* 7,figs4 #ha & #ha;,a7 %[s 7to a scale ( ab\t "o-qu>t] full size7 a complete outfit = elem5t>y electro/atic exp]im5ts1 su* z has be5 9 use 9 ! writ]'s laboratory = five ye>s4 ,) ^! appliances all ! fundam5tal exp]im5ts may be p]=m$1 & ! app>atus is always ready at a mom5t's notice4 ,fig4 #ha4 ,?\gh qu>tz does n cond5se moi/ure or gas to =m a conduct+ lay] ( any?+ l ! same conductivity z 9 ! case ( glass or ebonite1 /ill x is well to heat x if ! be/ results are to be obta9$4 ,= ?is purpose a small po9t$ bl[-pipe flame may be us$1 & ! rods may be got r$-hot )\t ! slighte/ dang] ( break+ !m4 ,!y !n rema9 p]fectly good & satisfactory = sev]al h\rs at lea/1 ev5 :5 expos$ to damp & du/y air4 ,! rods are conv5i5tly held 9 position by small brass f]rules1 into :i* !y are fa/5$ by a little pla/] ( ,p>is4 ,seal+-wax mu/ be avoid$1 on acc\nt ( ! inconv5i5ce x causes :5 ! heat+ ( ! rods is be+ c>ri$ out4 ,"o useful application ( fus$ qu>tz is to ! insulation ( galvanomet] coils 7,fig4 #hb71 ano!r to ! manufacture ( highly insulat+ keys 7,fig4 #hc72 :ile z an insulat+ susp5sion x has all ! virtues4 ,if x is desir$ to r5d] ! ?reads conduct+ !y may be lightly silv]$1 & w be f\nd to conduct well en\gh = electromet] "w be=e ! silv] coat+ is ?ick en\gh to s5sibly impair _! ela/ic prop]ties4 ,fig4 #ha;,a4 ,fig4 #hb is a full-size work+ draw+ ( a p>ticul> =m ( m\nt+ = galvanomet] coils4 ,! objects s\ght to be atta9$ are3 7#a7 high insulation ( ! coils1 7#b7 easy adju/m5t ( ! coils to ! susp5d$ sy/em4 ,! fir/ object is atta9$ z foll[s4 ,! ebonite r+ ,a is bor$ ) f\r radial holes1 ?r\gh :i* are slipp$ f ! inside ! fus$ qu>tz bolt-head$ p9s ,b4 ,! coil already soak$ 9 h>d p>aff9 is plac$ conc5trically 9 ! r+ ,a by means ( a special tempor>y c5t]+ /&4 ,! space betwe5 ! coil & ! r+ is fill$ up ) h>d p>aff91 & ?is holds ! qu>tz p9s 9 position4 ,! sy/em ( ebonite r+1 coil1 & p9s is !n fa/5$ into ! gun-metal coil c>ri]1 :i* is cut away entirely1 except ne> ! edges1 :]e x c>ries ! p9 brackets ,c4 ,^! brackets c swivel ab\t ! l[] fa/5+ at ,e be=e ! latt] is tight5$ up4 ,! coil is n[ adju/$ 9 ! adju/+ /& to be conc5tric ) ! axis ( symmetry ( ! coil c>ri]1 & ! support+ p9s are slipp$ into slot holes cut 9 ! brackets1 ! brackets be+ swivell$ z mu* z necess>y to all[ ( ?is4 ,:5 ! p9s are all ins]t$ ! brackets are screw$ up by ! screws at ,e4 ,! p9s are !n cem5t$ firmly to ! brackets by a little pla/] ( ,p>is4 ,! coil c>ri] c n[ be adju/$ to ! galvanomet] frame by means ( screws at ,d1 :i* pass ?r\gh wide holes 9 ! c>ri] & bold ! latt] 9 position by _! heads4 ,9 ! sectional plan ! p>ts ( ! galvanomet] frame are %[n %ad$4 ,! front ( ! frame at ,f ,f is ( glass1 & ! back ( ! frame is also made ( glass1 ?\gh ?is is n %[n 9 ! section4 ,a repres5ts an ebonite r+ into :i* ! wire coil is cem5t$ by means ( p>aff94 ,b ,b ,b ,b are qu>tz p9s1 ) heads inside ! ebonite r+4 ,c ,c ,c are slott$ brackets adju/able to ! p9s & capable ( rotation by releas+ ! screws ,e ,e4 ,d ,d are ! screws hold+ ! coil c>riage to ! galvanomet] framework4 ,^! screws pass ?r\gh l>ge holes 9 ! c>riage s z to all[ ( "s adju/m5t4 ,fig4 #hb4 ,fig4 #hc4 #ajd4 ,glass4 ,:5 glass is prop]ly *os5 & p]fectly dry x has insulat+ prop]ties possibly equal to ^? possess$ by qu>tz or cry/all9e sulphur4 ,= _m purposes1 h[ev]1 its usefulness is s]i\sly r$uc$ by ! p]si/5ce ) :i* x exhibits ! ph5om5a ( residual *>ge1 & ! difficulty t is exp]i5c$ 9 keep+ x dry4 ,! insulat+ p[] ( :ite fl9t glass is mu* 9 excess ( t ( s(t soda glass1 :i* is a poor insulator1 & ( ord9>y gre5 bottle glass4 ,! j>s ( ,"l ,kelv9's electromet]s1 :i* insulate v well1 are made ( :ite fl9t glass manufactur$ 9 ,glasg[1 b x is f\nd t occasionally a p>ticul> j> has to be reject$ on acc\nt ( its refus+ to insulate1 & ?is1 if ,i und]/& aright1 ev5 :5 x exhibits no visible defects4 ,a l>ge numb] ( v>ieties ( glass 7 te/$ by ,dr4 ,hopk9son at ,messrs4 ,*ance ,bros4 ,works1 9 #ahge & #ahgf 7,phil4 ,trans1 #ahgg71 & 9 #ahhg 7,proc4 ,roy4 ,soc4 xli4 #dec71 *iefly ) a view to ! elucidation ( ! laws regulat+ ! residual *>ge2 & incid5tally "s extraord9>ily high insulations 7 not$ among ! fl9t glasses4 ,! glass :i* gave ! smalle/ residual *>ge 0 an opal glass2 & fl9t glasses 7 f\nd to insulate #aje times z well z soda lime glasses4 ,! plates ( ,wim%ur/ ma*9es are made ( ord9>y %eet w9d[ glass1 b z ! insulat+ prop]ty ( ?is mat]ial appe>s to v>y1 x is g5]ally necess>y to clean1 dry1 & te/ a %eet be=e us+ x4 ,) reg>d to h>d ,bohemian glass1 ?is is /at$ by ,koell] 7,wi5 ,b]i*t7 to insulate t5 times z well z ! ord9>y ,?ur+ian s(t soda glass4 ,on ! :ole ! mo/ satisfactory laboratory practice is to employ good :ite fl9t glass4 ,! only po9t requir+ att5tion is ! prep>ation ( ! glass by clean+ & dry+4 ,( c\rse all grease or visible dirt mu/ be remov$ z describ$ 9 an e>li] *apt] 7 #ac71 b ?is is only a beg9n+4 ,! glass aft] be+ treat$ z describ$ & got into su* a /ate z to its surface t clean wat] no long] t5ds to dry (f unequally1 mu/ be subject$ to a fur!r scrub ) bibul\s pap] & a cle> solution ( oleate ( soda4 ,! glass is !n to be well r9s$ ) di/ill$ wat] & all[$ to dra9 on a %eet ( filt] pap]4 ,a v common cause ( failure lies 9 ! contam9ation ( ! glass ) grease f ! op]ator's f+]s4 ,be=e sett+ out to clean ! glass ! /ud5t w d well to wa% 8 h&s ) soap & wat]1 !n ) dilute ammonia & f9ally ) di/ill$ wat]4 ,9 ! case ( an electromet] j> :i* has become conduct+ b is n p]ceptibly dirty1 rubb+ ) a little oleate ( soda & a silk ribbon1 foll[$1 ( c\rse1 by copi\s wa%+1 does v well4 ,if !re is any t9-foil on ! j>1 great c>e mu/ be tak5 n to all[ ! glass surface to become contam9at$ by ! %ellac v>ni% or gum us$ to /ick ! t9-foil 9 position4 ,f9ally1 ! glass %\ld be dri$ by radiant heat & rais$ to a temp]ature ( #ajj ,c4 at lea/1 & kept at x = at lea/ half an h\r4 ,be=e dry+ x is ( c\rse advisable to all[ ! wat] to dra9 away z f> z possible1 & if ! wat] is only ! ord9>y di/ill$ wat] ( ! laboratory1 ! glass is pref]ably wip$ ) a clean bit ( filt] pap]2 any hairs :i* may be left ^u ! glass w bru% (f easily :5 ! glass is dry4 ,9 ord] to obta9 satisfactory results ! glass mu/ be plac$ 9 dry air be=e x has appreciably cool$4 ,?is is easily done 9 ! case ( electromet] j>s1 & s long z ! air rema9s p]fectly dry ?r\gh ! action ( sulphuric acid or phosphorus p5toxide1 ! j> w insulate4 ,! slighte/ :iff ( ord9>ily damp air w1 h[ev]1 enorm\sly r$uce ! insulat+ p[] ( ! glass1 s t unv>ni%$ glass surfaces mu/ be kept = app>atus :i* is practically air-tight4 ,= outside or imp]fectly protect$ uses ! glass does bett] :5 v>ni%$4 ,x is a fact1 h[ev]1 t v>ni%$ glass is r>ely if ev] s good z unv>ni%$ glass at its be/4 ,too mu* c>e _c be tak5 ov] ! prep>ation ( ! v>ni%2 ,fr5* poli%1 or c>elessly made %ellac v>ni%1 is likely to d m h>m ?an good4 ,! be/ orange %ellac mu/ be dissolv$ 9 good cold alcohol by %ak+ ! mat]ials toge!r 9 a bottle4 ,! alcohol is made suffici5tly pure by />t+ ) rectifi$ _s & dige/+ x 9 a t9 flask ov] quick-lime = sev]al days1 a rev]s$ cond5s] be+ atta*$4 ,a l>ge excess ( lime mu/ be employ$1 & ?is leads to a consid]able loss ( alcohol1 a mis=tune :i* mu/ be put up )4 ,aft]1 say1 ?irty h\rs' dige/ion1 ! alcohol may be di/ill$ (f & employ$ to act on ! %ellac4 ,9 mak+ v>ni%1 "t & tr\ble are sav$ by mak+ a good deal at "o op]ation--a ,w9*e/] full is a reasonable quantity4 ,! bottle may be fill$ ?ree-qu>t]s full ( ! %ellac flakes & !n fill$ up ) alcohol2 ?is gives a solution ( a conv5i5t /r5g?4 ,! solution1 h[ev]1 is by no means p]fect1 = ! %ellac conta9s insoluble matt]1 & ?is mu/ be got rid (f4' ,"o way ( do+ ?is is to filt] ! solution ?r\gh ! ?ick filt]+ pap] made by ,s*lei*] & ,s*uell = ! purpose1 b ! filt]+ is a sl[ process1 & h5ce requires to be conduct$ by a filt] pap] held 9 a clip 7n a funnel7 "u a bell j> to avoid evaporation4 ,ano!r & g5]ally m conv5i5t way 9 ! laboratory is to all[ ! muddy v>ni% to settle--a process requir+ at lea/ a mon?--& to decant ! cle> solution (f into ano!r bottle1 :]e x is kept = use4 ,! muddy residue works up ) ! next lot ( %ellac & alcohol1 :i* may be add$ at once = future use4 ,! glass to be v>ni%$ is w>m$ to a temp]ature (1 say1 #ej ,c1 & ! v>ni% put on ) a lacqu]+ bru%2 a ?9 uni=m coat is requir$4 ,! glass is left to dry long en\gh = ! %ellac to get ne>ly h>d & to all[ mo/ ( ! alcohol to evaporate4 ,x is !n heat$ be=e a fire1 or ev5 ov] a ,buns51 till ! %ellac s(t5s & beg9s to yield its fragrant *>act]i/ic smell4 ,if ! coat+ is too heavy1 or if ! heat+ is comm5c$ be=e ! %ellac is suffici5tly dry1 ! latt] w draw up into te>s1 :i* are unsightly & difficult to dry prop]ly4 ,on no acc\nt mu/ ! %ellac be all[$ to get ov]heat$4 ,if ! v>ni% is n q h>d :5 cold x may be assum$ to be do+ m h>m ?an good4 ,9 v>ni%+ glass tubes = insulat+ purposes x mu/ be rememb]$ t ! inside ( ! tube is seldom clos$ p]fectly z aga9/ ! ext]nal air1 & consequ5tly x also requires to be v>ni%$4 ,?is is be/ done by p\r+ 9 a little v>ni% consid]ably m dilute ?an t describ$1 & all[+ x to dra9 away z f> z possible1 aft] see+ t x has flood$ e "p ( ! tube4 ,dur+ ?is "p ( ! process ! upp] end ( ! tube mu/ be clos$1 or evaporation w g on s fa/ t moi/ure w be deposit$ f ! air ^u ! v>ni%$ surface4 ,aft]w>ds ! tube may be g5tly w>m$ & a curr5t ( air all[$ to pass1 s z to prev5t alcohol di/ill+ f "o "p ( ! tube to ano!r4 ,! tube is f9ally heat$ to ! s(t5+ po9t ( %ellac1 & if possible clos$ z f> z is practicable at once4 #aje4 ,ebonite or ,h>d ,rubb]4 ,?is exce$+ly useful sub/ance c be b\ght ( a p]fectly useless quality4 ,mu* ( ! ebonite =m]ly us$ to cov] induction coils = in/ance1 det]iorates s rapidly :5 expos$ to ! air t x requires to h its surface r5ew$ e few weeks4 ,! v be/ quality ( ebonite obta9able %\ld be solely employ$ 9 con/ruct+ electric works4 ,x is possible to pur*ase good ebonite f ! ,silv]t[n ,rubb] ,company 7& probably f o!r firms71 b ! price is necess>ily high1 ab\t f\r %ill+s p] p\nd or ov]4 ,at ord9>y temp]atures ebonite is h>d & brittle & breaks ) a well-m>k$ con*oidal fracture4 ,at ! temp]ature ( boil+ wat] ! ebonite becomes some:at s(t5$1 s t x is readily b5t into any desir$ %ape2 on cool+ x resumes its orig9al h>dness4 ,?is prop]ty ( s(t5+ at ! temp]ature ( boil+ wat] is a v valuable "o4 ,! ebonite to be b5t or flatt5$ is m]ely boil$ = half an h\r or s 9 wat]1 tak5 out1 br\ght to ! requir$ %ape z quickly z possible1 & left to cool clamp$ 9 position4 ,! %eet ebonite z x comes f ! mak]s is g5]ally f> f flat4 ,x is (t5 necess>y to flatt5 a %eet ( ebonite1 & ( c\rse ?is is ! m easily accompli%$ ! small] ! %eet4 ,consequ5tly a bit ( ebonite ( ab\t ! requir$ size is fir/ cut f ! /ock %eet by a hack-saw su* z is g5]ally us$ = metals4 ,?is piece is !n boil$ & press$ betwe5 two plan$ iron plates previ\sly w>m$ to ne> #ajj ,c4 ,) pieces ( ebonite su* z are us$ = ! tops ( resi/ance boxes1 measur+1 say1 #bj ,x #h ,x #aa in*es1 v little tr\ble is exp]i5c$4 ,! %eets :5 cold are f\nd to reta9 ! flatness :i* has be5 =c$ ^u !m p]fectly well4 ,x is o!rwise ) l>ge ?9 %eets su* z are us$ = ,holtz ma*9es4 ,i h succe$$ fairly1 b only fairly1 by press+ !m 9 a glu+ press1 consi/+ ( heavy plan$ iron slabs previ\sly heat$ to #ajj ,c4 ,i d n "k exactly h[ be/ to flatt5 v ?9 & l>ge %eets4 ,x is easy to make l>ge tubes out ( %eet ebonite by tak+ advantage ( ! s(t5+ :i* ebonite und]goes 9 boil+ wat]4 ,a wood5 m&rel is prep>$ ( ! prop] size & %ape4 ,! ebonite is s(t5$ & b5t r\nd x2 ?is may require two or ?ree op]ations1 = ! ebonite gets /iff v quickly aft] x is tak5 out ( ! wat]4 ,f9ally ! tube is b\nd r\nd ! m&rel ) suffici5t =ce to br+ x to ! prop] %ape & boil$ 9 wat]1 m&rel & all4 ,! ba? & its cont5ts are all[$ to cool toge!r1 s t ! ebonite cools uni=mly4 ,tubes made 9 ?is way are ( c\rse subject to ! drawback ( hav+ an unweld$ seam1 b !y d well en\gh to w9d wire ^u if v great accuracy ( =m is n requir$4 ,if v accurate spools are ne$$ ! m&rel is bett] made ( iron or slate & ! spool is turn$ up aft]w>ds4 ,! seam may be /rapp$ inside or at ! ends by bits ( ebonite act+ z bridges1 & ! seam itself may be caulk$ ) melt$ p>aff9 or an?rac5e4 ,work+ ,ebonite4 ,ebonite is be/ work$ z if x 7 brass1 ) ord9>y brass-turn+ or plan+ tools4 ,^! tools %\ld be z h>d z possible1 = ! edges are apt to suff] sev]ely1 & blunt tools leave a v undesirable woolly surface on ! ebonite4 ,9 turn+ or %ap+ ebonite %eets x is z well to beg9 by tak+ ! sk9 (f "o side fir/1 & !n rev]s+ ! %eet1 f9i%+ ! second side1 & !n return+ to ! fir/4 ,?is is on acc\nt ( ! fact t ebonite sometimes spr+s a little out ( %ape :5 ! sk9 is remov$4 ,turn$ "w 9 ebonite1 if well done1 requires no s&-pap]+1 b may be suffici5tly poli%$ by a h&ful ( its own %av+s & a little vasel9e4 ,! advantage ( us+ a poli%$ ebonite surface is t su* a surface det]iorates m sl[ly "u ! influ5ce ( light & air ?an a surface left r\gh f ! tool4 ,if v highly poli%$ surfaces are requir$1 ! ebonite aft] tool+ is work$ ) f9e pumice du/ & wat]1 appli$ on felt1 or :]e possible by means ( a felt buff on ! la!1 & f9ally poli%$ ) r\ge & wat]1 appli$ on felt or clo?4 ,ebonite works p>ticul>ly well "u a spiral mill+ cutt]1 & suffici5tly well "u an ord9>y r\nd$ plan+ tool1 ) cutt+ angle ! same z = brass1 & h>d5$ to ! lighte/ /raw col\r4 ,x is n possible1 on ! o!r h&1 to use ! c>p5t]'s plane ) success1 = ! angle ( ! tool is too acute & causes ! ebonite to *ip4 ,9 bor+ ebonite ! drill %\ld be )drawn f ! hole pretty (t5 & well lubricat$1 = if ! bor+s jam1 z !y are apt to d1 ! heat develop$ is v great & ! temp] ( ! drill gets spoil$4 ,ebonite w spoil a drill by heat+ z quickly z any?+ kn[n2 on ! o!r h&1 x may be drill$ v fa/ if prop] precaution is tak54 ,x is advisable to expose ebonite to ! light z little z possible1 especially if ! surface is unpoli%$1 = "u ! comb9$ action ( light & air ! sulphur at ! surface ( ! ebonite rapidly oxidises1 & ! ebonite becomes cov]$ ) a ?9 b highly conduct+ lay] ( sulphur\s or sulphuric acid or _! comp\nds4 ,:5 ?is happ5s ! ebonite may be improv$ by scrubb+ ) hot wat]1 or wa%+ freely ) alcohol rubb$ on ) cotton wa/e 9 ! case ( app>atus t _c be dism\nt$4 ,a complete cure1 h[ev]1 c only be effect$ by scrap+ (f ! out] lay] ( ebonite s z to expose a fre% surface4 ,= ?is purpose a bit ( %eet glass brok5 s z to leave a curv$ edge is v useful1 & ! ebonite is !n scrap$ l a cricket bat4 ,9 design+ app>atus = laboratory use x is z well to be> 9 m9d t soon] or lat] ! ebonite p>ts w require to be tak5 d[n & scrap$ up4 ,rods or tubes are1 ( c\rse1 mo/ quickly treat$ on ! la! ) r\gh glass clo?1 & may be f9i%$ ) f9e s&pap]1 !n pumice du/ & wat]1 appli$ on felt4 ,aft] clean+ ! pumice (f by means ( wat] & a rag1 ! f9al t\* may be giv5 by means ( vasel9e1 appli$ on clo? or on ebonite %av+s4 #ajf4 ,mica4 ,a great v>iety ( m9]als g "u ?is "n4 ,speak+ g5]ally1 ! ,russian micas com+ into comm]ce are pota% micas1 & mica pur*as$ 9 ,engl& may be tak5 to be pota% mica1 especially if x is 9 l>ge %eets4 ,at ord9>y temp]atures mica ( ! k9d f\nd 9 comm]ce is an excell5t insulator4 ,s*ultze 7,wi$4 ,ann4 vol4 xxxvi4 p4 #fee7 comes to ! conclusion t bo? at high & at l[ temp]atures mica 7( all k9ds87 is a bett] insulator ?an :ite mirror glass1 ! composition ( :i* is n /at$4 ,! exp]im5ts ( ! au?or ref]r$ to 7 app>5tly left unf9i%$1 & altoge!r too mu* /ress mu/ n be laid on ! results obta9$1 "o ( :i* 0 t mica conducts electrolytically to "s ext5t at high temp]atures4 ,b\ty 7,j\rnal de ,physique1 #ahij #i1 #bhh7 & ,j4 ,curie 7,?se de ,doctorat1 ,p>is1 #ahhh7 agree 9 mak+ ! f9al conductivity ( ! mica us$ 9 ,c>p5ti]'s cond5s]s exce$+ly small--at all ev5ts at ord9>y temp]atures4 ,be>+ 9 m9d t = su* sub/ances ! t]m specific resi/ance has no v def9ite mean+1 ,m4 ,b\ty consid]s x is n less ?an #c4ai x #ajbh ,e4,m4 units at ord9>y temp]atures4 ,m4 ,b\ty gives a note or illu/ration ( :at su* numb]s mean--a precaution n sup]flu\s 9 cases :]e magnitudes are d5ot$ log>i?mically4 ,ref]r+ to ! value quot$1 viz4 #c4ai x #ajbh1 ,m4 ,b\ty says1 ,ce s]ait la resi/ance d'une colonne de m]cure de #ammq de section et de longueur telle que la lumire se propageant dans le vide1 mettrait plus de #cjjj ans ,a se transmettre d'une extrmit ,i'autre de la colonne4 ,m4 ,b\ty returns to ! /udy ( mica 7muscovite7 9 ! ,j\rnal de ,physique = #ahib1 p4 #e1 & !re deals ) ! specific inductive capacity1 :i* = a v small p]iod ( *>ge he f9ds has ! value #h--;an enorm\s value = su* a good insulator1 & "o t x w\ld be desirable to v]ify by "s totally di/9ct me?od4 ,?is rem>k is en=c$ by ! fact t ,m4 ,klem5cic f9ds ! numb] #f = ! same con/ant4 ,! temp]ature coeffici5t ( ?is con/ant 0 too small = ,m4 ,b\ty to det]m9e4 ,! electric int5sity 0 ( ! ord] ( #ajj volts p] c5timetre1 & ! exp]im5ts seem to indicate t ! specific inductive capacity w\ld be only slightly less if ref]r$ to a p]iod ( *>ge indef9itely %ort4 ,i h f\nd t ! residual *>ge 9 a mica cond5s]1 made accord+ to ,c>p5ti]'s me?od 7to be describ$ bel[71 is ab\t #a p] c5t ( ! orig9al *>ge "u ! foll[+ circum/ances4 ,voltage #cjj volts on a plate #j4b mm4 ?ick1 duration ( *>ge t5 m9utes1 temp]ature ab\t #bj ,c4 ,to get ?is result ! mica mu/ be mo/ c>efully dri$4 ,?is & o!r facts indicate t ! s-call$ residual *>ge on ord9>y cond5s]s is1 to a v l>ge ext5t1 due to ! creep+ ( ! *>ge f ! armatures ov] ! m or less conduct+ v>ni%$ surfaces ( ! mica1 & its sl[ return on dis*>ge4 ,?is s\rce ( residual *>ge 0 c>efully gu>d$ aga9/ by ,r[l& & ,ni*ols 7,phil4 ,mag4 #ahha7 9 _! "w on qu>tz1 & is ref]r$ to by ,m4 ,b\ty1 :o adduces "s exp]im5ts to %[ t 8 own results are n vitiat$ by x4 ,on ! o!r h&1 ,m4 ,b\ty %[s t a small rise 9 temp]ature enorm\sly affects ! /ate ( a mica surface1 & t ! surface gets *ang$ 9 su* a way z to become v fairly conduct+ at #cjj ,c4 ,also anybody c easily try = himself :e!r expos+ a mica cond5s] plate :i* has be5 exam9$ 9 pres5ce ( phosphorus p5toxide to ord9>y air = five m9utes w n enorm\sly increase ! residual *>ge1 z has always be5 ! case 9 ! writ]'s exp]i5ce1 & if s1 x is op5 to him to sugge/ "s cause o!r ?an surface creep+ z an explanation4 ,m4 ,b\ty1 us+ less p]fectly dri$ mica1 did n get s good a result z to smallness ( residual *>ge z ! "o above quot$4 ,! *ief use ( mica = laboratory purposes dep5ds on ! ease ) :i* x c be split1 & also ^u ! fact t x may be consid]ably crumpl$ & b5t )\t break+4 ,x !re=e makes an excell5t dielectric 9 s f> z conv5i5ce ( con/ruction is conc]n$ 9 ! prep>ation ( cond5s]s1 & l5ds itself freely to ! con/ruction ( insulat+ wa%]s or sep>ators ( any k9d4 ,its success z a fair insulator at mod]ate temp]atures has l$ to its use 9 resi/ance !rmomet]s1 :]e x appe>s to h giv5 satisfaction up to1 at all ev5ts1 #djj ,c4 ,x is wor? a note t accord+ to ,w]n] ,siem5s1 :o _h imm5se exp]i5ce 7,wi$4 ,ann4 vol4 clix471 soap/one is ! only reliable insulator at a r$ heat1 b1 no d\bt1 a good deal dep5ds on ! p>ticul> specim5 inve/igat$4 #ajg4 ,use ( ,mica 9 ,cond5s]s4 ,if good results are desir$ x is ess5tial to select ! mica v c>efully4 ,pieces appreciably /a9$1--p>ticul>ly if ! /a9 is n uni=mly di/ribut$1--crack$ pieces1 & pieces t5d+ to flake (f 9 pat*es %\ld be reject$4 ,! be/ samples ( mica t h come "u ! writ]'s obs]vation are ^? %eets sold = ! purpose ( giv+ to silv] photographic pr9ts t hide\s glaz$ surface :i* "s ye>s ago 0 s popul>4 ,%eets ( mica ab\t #j4a to #j4b mm4 ?ick =m good s]viceable cond5s] plates1 & w c]ta9ly /& a pressure ( #cjj volts1 & mo/ likely a good deal m4 ,! g5]al practice 9 ,engl& seems to h be5 to build up cond5s]s ( alt]nate %eets ( v>ni%$ or p>aff9$-mica & t9-foil4 ,?is practice is op5 to sev]al objections4 ,9 ! fir/ place1 ! capacity ( a cond5s] made 9 ?is way v>ies ) ! pressure b9d+ ! plates toge!r4 ,9 ! second place1 ! am\nt ( mica & t9-foil requir$ is (t5 excessive 9 consequ5ce ( ! imp]fect contact ( ^! sub/ances4 ,aga91 ! inevitable air film betwe5 ! mica & t9-foil r5d]s cond5s]s s made unsuitable = use ) alt]nat+ curr5ts1 ow+ to ! heat+ set up ?r\gh air dis*>ges1 & :i* is g5]ally1 ?\gh (t5 7if n always7 wrongly1 attribut$ to dielectric hy/]esis4 ,^! imp]fections are to a great ext5t got ov] by ,m4 ,c>p5ti]'s me?od ( con/ruction1 :i* is1 h[ev]1 r m co/ly bo? 9 mat]ial & lab\r4 ,on ! o!r h&1 wond]ful capacities are obta9$ ) q small am\nts ( mica4 ,m4 ,b\ty m5tions a cond5s] ( "o micr(>ad capacity weigh+ #aejj grms4 & conta9$ 9 a squ>e box measur+ #ab c5timetres on ! side1 & ab\t #c c5timetres ?ick4 ,! relation betwe5 ! capacity & surface ( d\bly-coat$ plates is 9 electro-/atic units3 ,capacity 7sp4 ind4 capacity ,x area ( "o surface7_/7#dpi ,x ?ickness7 ,?is may be r$uc$ to electro-magnetic units by divid+ by #ix#ajbj1 & to micr(>ads by fur!r multiply+ by #ajae4 ,m4 ,c>p5ti] beg9s1 ( c\rse1 by hav+ 8 mica scrupul\sly clean & well select$4 ,x is !n silv]$ by "o ( ! silv]+ processes 7 #fe7 on bo? sides1 = :i* purpose ! %eets may be susp5d$ 9 a p>aff9$ wood rack1 s z to lie horizontally 9 ! silv]+ solution1 a space ( ab\t half an in* be+ all[$ betwe5 ! %eets4 ,! silv]+ be+ f9i%$1 ! %eets are dipp$ along two p>allel edges 9 #ge p] c5t nitric acid4 ,) reg>d to ! ?ird & f\r? edges ( ! %eet1 ! silv] is remov$ on "o side only1 us+ a spun glass bru%2 if we agree to call ! two surfaces ( ! mica ,a & ,b respectively1 & ! two edges 9 "q ,c & ,d1 !n ! silv] is remov$ f ! ,a side along edge ,c1 & f ! ,b side along edge ,d4 ,! silv]$ "p is %[n %ad$ 9 ,fig4 #hd4 ,by ?is arrangem5t ! silv] & mica plates may be built up toge!r s z to =m ! same mutual arrangem5t ( contacts z 9 an ord9>y mica t9-foil cond5s]4 ,fig4 #hd4 ,x ne$ h>dly be said t ! %eets require v complete wa%+ aft] treatm5t ) nitric acid1 foll[$ by a v>ni%+ ( ! edges z already describ$ 9 ! case ( glass1 & bak+ at a temp]ature ( #adj ,c4 9 air free f flame gases1 till ! %ellac beg9s to emit its *>act]i/ic od\r & is absolutely h>d :5 cold4 ,! plates are !n built up s z to connect ! %eets :i* require to be connect$1 & to insulate ! o!r set4 ,g5]al contact is1 if necess>y1 secur$ by means ( a little silv] leaf loop$ across f plate to plate--a "p ( ! con/ruction :i* requires p>ticul> att5tion & clean h&s1 = x is by no means s easy to make an unimpea*able contact z might at fir/ appe>4 ,! cond5s]1 hav+ be5 built up1 may be clamp$ solid & plac$ 9 its case2 ! capacity w n dep5d appreciably on ! tightness ( ! clamp screws--a great feature ( ! con/ruction4 ,su* a cond5s] w n give its be/ results unless absolutely dry4 ,i h kept "o v conv5i5tly 9 a vacuum desiccator ov] phosphorus p5toxide1 b if ( any size1 ! cond5s] des]ves a box to itself1 & ?is mu/ be air-tight & provid$ ) a dry+ reag5t1 s arrang$ t x c be remov$ ?r\gh a manhole ( "s sort4 ,contact to ! brass-"w on ! lid may be made by press+ spr+ contacts tightly d[n ^u ! ends ( ! silv] foils & c>ry+ ! connections ?r\gh ! lid4 ,?is also s]ves to secure ! cond5s] 9 position4 #ajh4 ,micanite4 ,?is sub/ance1 ?\gh probably comp>+ some:at unfav\rably ) ! insulators already enum]at$1 & be+ subject to ! unc]ta9ties ( manufacture1 has dur+ ! la/ few ye>s a*iev$ a consid]able success 9 ,am]ican electrical eng9e]+ con/ruction4 ,x is compos$ ( scrap mica & %ellac v>ni% work$ "u pressure to ! desir$ %ape1 & may be obta9$ 9 %eets1 plates1 & rods1 or 9 any ( ! =ms = :i* a die happ5s to h be5 con/ruct$4 ,( c\rse1 9 special cases x w\ld be wor? :ile to prep>e a die1 & !n ! atta9able =ms w\ld be limit$ by m\ld+ consid]ations only4 ,! writ]'s exp]i5ce is v limit$ 9 ?is matt]1 b ,dr4 ,k5nelly1 ) :om he communicat$ on ! subject1 0 good en\gh to reply 9 fav\r ( micanite = eng9e]+ "w4 #aji4 ,celluloid4 ,?is mat]ial is compos$ ( nitrocellulose & camphor4 ,x has fair insulat+ prop]ties1 & may be obta9$ 9 a v>iety ( =ms1 b has n[ be5 g5]ally ab&on$ = electrical "w on acc\nt ( its inflammability4 #aaj4 ,pap]4 ,pure :ite filt] pap]1 p]fectly dry1 is probably a v fair insulator2 ! mis=tune is t 9 practice x _c be kept dry4 ,"u ! mo/ fav\rable circum/ances its specific resi/ance may approa* #ajbd ,e4,m4 units4 ,x mu/ !re=e be consid]$ r z a p>tial conductor ?an z an insulator4 ,! only case ( ! use ( dry pap] z an insulator 9 ma*9e con/ruction :i* has come "u ! writ]'s notice is 9 build+ up ! commutators ( ! small motors :i* us$ to drive ! ,edison phonographs4 ,its advantages 9 ?is connection are to be trac$ to ! fact t a commutator s built up is durable & keeps a clean surface4 ,( c\rse1 ! use ( pap] z an insulator = telephone wires is well kn[n1 b its success 9 ?is direction dep5ds less ^u its insulat+ prop]ties ?an ^u ! fact t x c be arrang$ 9 su* a way z to all[ ( ! wires be+ p>tially air insulat$1 an arrangem5t t5d+ to r$uce ! electro/atic capacity ( ! wire sy/em4 ,at "o "t x 0 ! cu/om ( in/rum5t mak]s to employ ord9>y pr9t$ pap] 9 ! %ape ( leaves torn f books or ! folios ( old l$g]s to =m ! dielectric ( ! cond5s]s us$ 9 connection ) ! contact break]s ( induction coils4 ,?is practice has no?+ b economy to recomm5d x1 = cases (t5 occur 9 :i* ! pap]1 by gradual absorption ( moi/ure f ! air1 comes to insulate s badly t x practically %ort circuits ! sp>k gap1 & s /ops ! action ( ! coil4 ,?ree sep>ate cases h come )9 ! writ]'s exp]i5ce4 ,"s measurem5ts ( ! resi/ance ( pap] h be5 made by ,f4 ,upp5born 7,c5tralblatt fu] ,electrote*nik1 ,vol4 xi4 p4 #bae1 #ahhi74 ,!re is an ab/ract ( ! pap] also 9 ,wi$emann's ,beiblaett] 7#ahhi1 vol4 xiii4 ,p4 #gaa74 ,upp5born exam9$ ! samples ( pap] "u normal conditions z to moi/ure & obta9$ ! foll[+ results3- ,description ( ,pap] ,i ,pressure ,int5sity ,,ii4 ,specific ,resi/ance correspond+ to pressures z 9 ,column ,i4 ,ohms4 ,,iii ,pressure ,int5sity4 ,,iv4 ,specific ,resi/ance correspond+ to ,column ,,iii4 ,ohms4 ,common c>dbo>d #b4c mm4 ?ick #j4je kilo4 p] #fjjj sq4 mm4 #d4he x #ajae #bj kg4 p] #fjjj sq4 mm4 #d4g x #ajad ,gray pap]1 #j4bf mm4 ?ick #j4je kilo4 p] #ejjj sq4 mm4 #c4a x #ajae #bj kg4 p] #ejjj sq4 mm4 #h x #ajad ,yell[ p>*m5t pap]-#ji mm4 ?ick #j4je kilo4 p] #ecjj sq4 mm4 #c4je x #ajaf #bj kg4 p] #ecjj sq4 mm4 #h x #ajaf ,l95 trac+ clo? #j4je kilo4 p] #fjjj sq4 mm4 #a4ce x #ajaf #bj kg4 p] #cc1jjj sq4 mm4 #a4hf x #ajae #aaa4 ,p>aff9$ ,pap]4 ,l wood & o!r semiconductors1 pap] c be va/ly improv$ z an insulator by saturat+ x ) melt$ p>aff94 ,to get ! be/ results a pure pap] free f size mu/ be employ$--gray ,sw$i% filt] pap] does well4 ,?is is dri$ at a temp]ature above #ajj ,c4 =1 say1 half an h\r1 & ! %eets are !n float$ on ! top ( p>aff91 kept melt$ at #adj ,c4 or !reab\t 9 a bak+ di%4 ,z soon z ! pap] is plac$ ^u ! melt$ p>aff9 ! latt] beg9s to soak ?r\gh1 9 virtue ( capill>y action1 & drives be=e x ! air & moi/ure1 caus+ a /rongly m>k$ eff]vesc5ce4 ,aft] ab\t "o m9ute ! pap] may be ?ru/ bel[ ! p>aff9 to soak4 ,:5 a suffici5t numb] ( pap]s h accumulat$1 & :5 no m gas comes (f1 ! tray may be plac$ 9 a vacuum box 7,fig4 #he71 & ! pressure r$uc$ by ! filt] pump4 ,z ! removal ( ! air takes "t1 provision mu/ be made = keep+ ! ba? hot4 ,a vacuum may be ma9ta9$ = ab\t an h\r1 & air !n readmitt$4 ,repeat$ exhau/ions & readmissions ( air1 :i* appe> to improve wood1 d n give any?+ l su* a good result ) pap]4 ,9 us+ a vacuum box provision mu/ be made 9 ! %ape ( a cool bottle betwe5 ! air pump & ! box4 ,if ?is precaution be omitt$1 & if any p>aff9 spla%es on to ! hot surface ( ! box1 x volatilises ) decomposition & ! products g to /op up ! pump4 ,p>aff9 ) a melt+-po9t ( #ej ,c4 or upw>ds does well4 ,! ba? %\ld be all[$ to cool to ab\t #fj ,c4 be=e ! pap]s are remov$1 s t en\gh p>aff9 may be c>ri$ out to ?or\ghly coat ! pap] & prev5t ! entrance ( air4 ,fig4 #he4 ,fig4 #he is a section ( a vacuum vessel :i* has be5 f\nd v conv5i5t4 ,x measures ab\t two feet 9 diamet] at ! top4 ,x is r\nd1 because x is mu* easi] to turn "o circul> surface ?an to plane up f\r surfaces1 :i* has to be done if ! box is squ>e4 ,bo? ! rim ( ! vessel & ! approximat+ "p ( ! cov] require to be truly turn$ & smoo?ly f9i%$4 ,a v good pack+ is made ( solid indi>ubb] core ab\t half an in* ?ick4 ,?is is c>efully splic$--cem5t$ by means ( a solution ( rubb] 9 naph?a1 & ! splice sew$ by ?ick ?read4 ,! lid ought to h a rim fitt+ inside ! vessel1 = ?is keeps ! rubb] pack+ 9 place2 ! rim has be5 accid5tally omitt$ 9 ,fig4 #he4 ,! bolts %\ld n be m ?an five in*es ap>t1 & %\ld lie at lea/ half an in* 9 diamet]1 & ! rim & lid %\ld be ea* half an in* ?ick4 ,cond5s]s may n[ be built up ( %eets ( ?is prep>$ pap] int]leav$ ) t9-foil 9 ! ord9>y way4 ,if good results are requir$1 ! cond5s] :5 f9i%$ is compress$ betwe5 wood5 or glass end-pieces by means ( suitable clamps4 ,x c !n be put 9 a box ( melt$ p>aff91 heat$ up to #adj ,c1 & exhau/$ by means ( ! wat] pump = sev]al h\rs4 ,9 ?is process ! air ru%es out f betwe5 ! pap] & foils ) su* vehem5ce t ! p>aff9 is g5]ally ?r[n entirely out ( ! box4 ,to gu>d aga9/ ?is ! box mu/ be provid$ ) a loosely fitt+ & tempor>y lid1 pi]c$ ) sev]al holes4 ,! real te/ z to :5 exhau/ion is complete w\ld be ! cessation ( any yield ( air or wat]4 ,s9ce x is n g5]ally conv5i5t to make ! vacuum box s air-tight t !re are absolutely no leaks at all1 & z ! p>aff9 itself is1 ,i ?9k1 incl9$ to crack slightly at ! temp]ature ( #adj ,c1 ?is te/ or crit]ion _c be conv5i5tly appli$4 ,two exhau/ions1 ea* ( ab\t two h\rs' duration1 h1 h[ev]1 9 my exp]i5ce succe$$ v well1 provid$1 ( c\rse1 t ! dielectric is prep>$ z sugge/$4 ,at ! end ( ! exhau/ion process ! clamp+ screws are tight5$ z f> z possible1 ! cond5s] rema9+ 9 its ba? until ! p>aff9 is pa/y4 ,cond5s]s made 9 ?is way resi/ ! application ( alt]nat+ curr5ts p]fectly1 z ! foll[+ te/s w %[4 ,! dielectric consi/$ ( ab\t equal p>ts ( h>d p>aff9 & vasel9e4 ,a cond5s] ( ab\t #j4abc micr(>ads capacity & an insulation resi/ance ( #bjjj megohms1 ,footnote3 ,z te/$ by a small voltage4 hav+ a t9-foil area ( #d4bc squ>e metres 7ab\t71 & d\ble pap]s ea* ab\t #j4b mm4 ?ick1 design$ to run at #bjjj volts ) a frequ5cy ( #fc complete p]iods1 0 te/$ at ?is frequ5cy4 ,! cond5s] 0 ?or\ghly pack$ all r\nd 9 cotton-wool to a ?ickness ( #f in*es1 & its temp]ature 0 indicat$ m or less by a !rmomet] plung$ ?r\gh a hole 9 ! lid ( ! conta9+ box & ( ! cond5s] box1 & re/+ on ! upp] surface ( "o set ( t9-foil electrodes1 f :i* ! s(t p>aff9 mixture _h be5 purposely scrap$ away4 ,! foll[+ 7 ! results ( a f\r h\rs' run at a voltage #ej p] c5t high] ?an t = :i* ! cond5s] 0 design$--i4e4 #cjjj volts4 ,times4 ,voltage ,temp]ature ,temp]ature ,diff]5ce 9 ,cond5s]4 9 ,air4 ,hrs4 ,m94 #b #aj #bgej #bb4h ,c4 #bc4j ,c4 #j4b #c #aj #bgjj #bc4j ,c4 #bc4c ,c4 #j4c #c #ah #cbjj #bc4a ,c4 #bc4j ,c4 -#j4a #d #aj #cbjj #bc4c ,c4 #bc4g ,c4 #j4d #e #aj #cajj #bc4f ,c4 #bc4d ,c4 -#j4b #f #aj #cjjj #bc4h ,c4 #bc4ce ,c4 -#j4de ,an idea ( ! ord] ( ! am\nt ( wa/e may be =m$ f ! foll[+ additional exp]im5t4 ,a cond5s] simil> to ! "o describ$ 0 fill$ ) oil ( a l[ insulat+ p[]4 ,x 0 te/$ calorimetrically1 & also by ! ?ree voltmet] me?od1 :i*1 h[ev]1 prov$ to be too ins5sitive4 ,! temp]ature rise 9 ! non-conduct+ box 9 air 0 ab\t #j4c ,c4 p] h\r1 & ! loss ( p[] 0 f\nd to be less ?an #j4a p] c5t4 ,9 ! pres5t case ! actual rise 0 only #a 9 f\r h\rs1 & ! integral give & take betwe5 ! cond5s] & ! air is practically no?+2 consequ5tly we may consid] ) safety t ! rate ( rise is c]ta9ly less ?an #a degree p] ?ree h\rs4 ,! voltage & frequ5cy 7 ab\t ! same 9 bo? exp]im5ts1 consequ5tly ! en]gy pass$ is ab\t proportional to ! capacity us$ 9 ! two exp]im5ts4 ,f ?is x foll[s t s9ce ! specific heat ( bo? cond5s]s 0 ! same 7ne>ly71 ! loss 9 ! pres5t case is a good deal less ?an "o-t5? p] c5t4 ,! residual *>ge is also mu* less ?an :5 ! cond5s] is simply built up ( pap] p>aff9$ 9 an unsy/ematic mann]1 & f :i* ! air & wat] h be5 imp]fectly extract$1 z by bak+ ! cond5s] fir/1 & !n imm]s+ x 9 p>aff9 or oil4 ,x is usual to consid] t ! ph5om5a ( residual *>ge & heat+ 9 cond5s]s1 to :i* alt]nat+ voltages are appli$1 are closely alli$4 ,?is is true1 b ! alliance is n "o betwe5 cause & effect--at all ev5ts1 ) reg>d to ! great] "p ( ! heat+4 ,! imp]fect exclusion ( air & moi/ure1 p>ticul>ly ! latt]1 c]ta9ly increases ! residual *>ge by all[+ surface creep+ to occur2 b x also acts directly 9 produc+ heat+1 bo? by l[]+ ! insulation ( ! cond5s] & by all[+ ( air dis*>ges betwe5 ! cond5s] plates4 ,( ^! causes ( heat+1 ! dis*>ges 9 air or wat] vap\r are probably ! m important4 ,long ago a !ory ( residual *>ge 0 giv5 by ,maxwell1 bas$ on ! consid]ation ( a lam9at$ dielectric1 ! inductivity & resi/ance ( :i* v>i$ f lay] to lay]4 ,x 0 %[n t su* an arrangem5t1 & h5ce g5]ally any want ( homog5eity 9 a direction incl9$ to ! l9es ( =ce lead+ to a *ange ( value ( ! product ( specific resi/ance & specific inductive capacity1 w\ld acc\nt = residual *>ge4 ,?is possible explanation has be5 g5]ally accept$ z ! actual explanation1 & _m cases ( residual *>ge attribut$ to want ( homog5eity1 :i* are c]ta9ly to be expla9$ 9 a simpl] mann]4 ,= in/ance1 ! residual *>ge 9 a silv]$ mica plate cond5s]1 c>efully dri$1 c be increas$ at lea/ t5fold by an exposure ( a few m9utes to ord9>ily damp air4 ,! same result occurs ) cond5s]s ( p>aff9$ or sulphur$ pap]2 & ^! are ! residual *anges g5]ally obs]v$4 ,! great] "p mu/ be due to creep+4 #aab4 ,p>aff94 ,?is sub/ance has long enjoy$ great popul>ity 9 ! physical laboratory4 ,its specific resi/ance is giv5 by ,ayrton & ,p]ry z m ?an #ajbe1 b x is probably mu* high] 9 select$ samples4 ,! mo/ s]viceable k9d ( p>aff9 is ! h>de/ obta9able1 melt+ at a temp]ature ( n less ?an #eb ,c4 ,x is a good plan to remelt ! comm]cial p>aff9 & keep x at a temp]ature (1 say1 #abj ,c4 = an h\r1 /irr+ x c>efully ) a glass rod s t x does n get ov]heat$2 ?is helps to get rid ( traces ( wat] vap\r4 ,h>d p>aff91 :5 melt$1 has an enorm\s rate ( expansion ) temp]ature1 s great1 inde$1 t c>e mu/ be tak5 n to ov]fill ! vessels 9 :i* x is to be heat$4 ,ca/+s c only be prep>$ by cool+ ! m\ld sl[ly f ! bottom1 keep+ ! re/ ( ! m\ld w>m1 & add+-p>aff9 f "t to "t to make up = ! contraction4 ,! cool+ is gradually all[$ to spread up to ! free surface4 ,! *ief use ( p>aff9 9 ! laboratory is 9 ! con/ruction ( complicat$ connection bo>ds1 :i* are easily made by drill+ holes 9 a slab ( p>aff91 half fill+ !m ) m]cury1 & us+ !m z m]cury cups4 ,s9ce p>aff9 is a great collector ( du/1 x %\ld be scre5$ by pap]1 o!rwise ! blocks require to be scrap$ at frequ5t int]vals1 :i*1 ( c\rse1 electrifies !m consid]ably4 ,?is electrification is (t5 difficult to remove )\t injur+ ! insulat+ p[] ( ! p>aff94 ,a light t\* ) a clean ,buns5 flame is ! readie/ me?od1 & does n appe> to r$uce ! insulation s mu* z might be expect$4 ,! safe/ way1 h[ev]1 is to leave ! key cov]$ by a clean clo?1 :i*1 h[ev]1 mu/ n t\* ! surface1 = a suffici5t "t to all[ ( ! *>ges gett+ away4 ,! p>aff9 (t5 becomes electrifi$ itself by ! friction ( ! key contacts1 s t 9 electromet] "w x is (t5 conv5i5t to =m ! cups by l9+ !m ) a little roll ( copp] foil twi/$ up at ! bottom4 ,9 ?is case ! connect+ wires %\ld1 ( c\rse1 be copp]4 ,small /eel /aples are conv5i5t = fa/5+ ! collect+ wires ^u ! p>aff92 or1 9 ! case :]e ^! wires h to be (t5 remov$ & *ang$ ab\t1 draw+-p9s are v h&y4 ,) m]cury cups simply bor$ 9 p>aff9 great tr\ble w (t5 be exp]i5c$ 9 electromet] "w1 ow+ to a pot5tial diff]5ce appe>+ betwe5 ! cups--at all ev5ts :5 ! contacts are ins]t$ & h[ev] c>efully ?is be done4 ,a few drops ( v pure alcohol p\r$ 9 above ! m]cury (t5 cures ?is defect4 ,! surface ( p>aff9 is by no means exempt f ! defect ( los+ its insulat+ p[] :5 expos$ to damp air1 b x is n s s5sitive z glass1 nor does ! insulat+ p[] fall s f>4 ,two useful appliances are figur$4 ,fig4 #hf4 ,fig4 #hg4 ,"o1 9 :i* p>aff9 appe>s z a cem5t1 is an insulat+ /& made out ( a bit ( glass or ebonite tube cem5t$ into an ,erl5mey] flask1 hav+ its neck protect$ f du/ :5 out ( use by a rubb] wa%]1 ! o!r a petticoat insulator made by cem5t+ a fl9t glass bottle into a glass di% ) p>aff94 ,9 c\rse ( "t ! p>aff9 w be f\nd to h sep>at$ f ! glass4 ,:5 ?is occurs ! app>atus may be melt$ toge!r aga9 by plac+ x on ! wat] ba? = a few m9utes4 #aac4 ,vasel9e1 ,vasel9e ,oil1 & ,k]os5e ,oil4 ,^!1 :5 dry1 insulate almo/1 b n q z well z solid p>aff94 ,h4 ,koell] 7,wi5 ,b]i*te1 #ih1 ii4 #bja1 #ahhi2 ,beibl4 ,wi$4 ,ann4 #ahij1 p4 #ahf71 work+ ) v small voltages1 places ! f9al787 specific resi/ance ( comm]cial petroleum1 e!r1 & vasel9e oil at ab\t #b ,x #ajbg ,c4,g4,s4 ,?is is t5 times high] ?an ! value assign$ to comm]cial b5z5e 7,c#f;,h#f71 & a hundr$ times high] ?an ! value = comm]cial tolu5e4 ,all ^! numb]s mean little or no?+1 b ! petroleum & vasel9e oil 7 ! be/ fluid insulators exam9$ by ,koell]4 ,by mix+ vasel9e ) p>aff9 a s(t wax may be made ( any desir$ degree ( s(tness1 & by dissolv+ vasel9e 9 k]os5e an insulat+ liquid ( any degree ( viscidity may be obta9$4 ,h>d p>aff9 may be s(t5$ some:at by ! addition ( k]os5e1 & an app>5tly homog5e\s mass ca/ f ! mixture4 ,x w be f\nd1 h[ev]1 t 9 c\rse ( "t ! k]os5e oozes out1 unless pres5t 9 v small quantity4 ,koell] has f\nd 7loc4 cit47 t "s samples ( vasel9e oil conduct$ voll/a5dig gut1 b ,i h n come across su* samples4 ,vasel9e oil1 h[ev]1 is sold at a price mu* above its value = insulat+ purposes4 ,k]os5e oil is be/ obta9$ dry by draw+ x directly f a new t9 & expos+ x to air z little z possible4 ,( c\rse1 x may be dri$ by *emical means & di/illation1 b ?is is usually 7or always7 unnecess>y4 ,fig #hh4 ,!re is "s dang] ( k]os5e conta9+ m9ute traces ( sulphuric acid1 & x & o!r oils may be conv5i5tly te/$ = insulation 9 ! foll[+ mann]4 ,! qu>tz electroscope is tak51 & ! insulat+ rod heat$ 9 ! bl[-pipe4 ,! electroscope w n[ insulate well en\gh to %[ no appreciable collapse ( ! leaves 9 "o or two h\rs' "t4 ,^u ! plate ( ! electroscope is put a plat9um or copp] cyl9d]1 & ?is is fill$ ) k]os5e 7say7 up to a fix$ m>k4 ,! electroscope is plac$ on a surface plate1 or1 at all ev5ts1 on a %eet ( plate glass1 & a scrib+ block is plac$ along side x & ! scrib] adju/$ to dip into ! k]os5e to any requir$ dep?4 ,?is is done by twi/+ a bit ( wire r\nd ! scrib+ po9t & all[+ x to project d[nw>ds4 ,! po9t itself s]ves to give an idea ( ! height to :i* ! vessel may be fill$4 ,! liquid is adju/$ till its surface is 9 contact ) ! end ( ! scrib+ po9t1 & ! wire !n projects into ! liquid & =ms an electrode ( con/ant area ( surface4 ,! scrib+ block is put to e>?4 ,a *>ge is giv5 to ! electroscope1 & ! "t requir$ = a giv5 degree ( collapse ( ! leaves not$4 ,! k]os5e is !n remov$ & its place tak5 by vasel9e or p>aff91 kn[n to insulate well z a /&>d = comp>ison4 ,! exp]im5t is !n repeat$1 & ! "t not$ = ! same degree ( collapse4 ,?is te/1 ?\gh ( c\rse r\gh1 is g5]ally q suffici5t = work%op purposes1 & is easily appli$4 ,moreov]1 x does n require correction = electromet] leakage1 z g5]ally happ5s :5 m elaborate appliances are us$4 ,! actual resi/ance ( insulat+ oils dep5ds s mu* on ! electrical int5sity1 on ! duration ( t int5sity1 & on ! previ\s hi/ory ( ! oil z to ! direction ( ! voltage to :i* x has be5 subject$--to say no?+ ( ! effects ( traces ( moi/ure--t quantitative exp]im5ts are ( no value unless !y are extremely elaborate4 ,i %all !re=e only app5d ! foll[+ numb]s due to ,b\ty1 ,ann4 de ,*emie et de ,physique 7#f71 vol4 xxvii4 p4 #fb1 #ahib1 9 :i* ! effect ( ! conductivity on ! det]m9ation ( ! specific inductive capacity 0 prop]ly all[$ =3- ,c>bon ,bisulphide4 ,turp5t9e4 ,b5z5e 7,c#f;,h#f7 at #bj ,c4 ,b5z5e at #fj ,c4 ,specific inductive capacity #b4gae #b4cad #b4ba #b4bb ,specific resi/ance 9 ohms p] cubic c5timetre #a4e x #ajac1 #a4ge x #ajab #a4ef x #ajaa #g4i x #ajaa ,footnote3 ,pr(essor ,j4 ,j4 ,?omson1 & ,newall 7,phil4 ,proc4 #ahhf7 consid] t c>bon bisulphide %[$ traces ( a residual *>ge effect2 h5ce1 until ?is po9t is cle>$ up1 we mu/ reg>d ,b\ty's value z correspond+ only to a v %ort1 b n indef9itely %ort1 p]iod ( *>ge4 ,on ?is po9t ! pap] mu/ be consult$4 ,m>* #ahig--,! writ] has inve/igat$ ?is po9t by an indep5d5t me?od1 b f\nd no traces ( residual *>ge4 ,in=mation z to ! specific inductive capacity ( a l>ge numb] ( oils may be f\nd 9 a pap] by ,hopk9son1 ,phil4 ,proc4 #ahhg1 & 9 a pap] by ,qu9cke 9 ,wi$emann's ,annal51 #ahhc4 #aad4 ,imp]fect ,conductors4 ,"u ?is head+ may be gr\p$ su* ?+s z wood1 slate1 m>ble1 etc--9 fact1 mat]ials g5]ally us$ = swit*bo>d insulation4 ,an exam9ation ( ! insulat+ p[] ( ^! sub/ances has rec5tly be5 made by ,b4 ,o4 ,peirce 7,electrical ,review1 #aa? ,janu>y #ahie7 ) q suffici5t accuracy1 hav+ 9 view ! impossibility ( be+ c]ta9 be=eh& z to ! "* ( any p>ticul> sample4 ,! te/s 7 made by means ( holes drill$ 9 slabs ( ! mat]ial to be exam9$4 ,^! holes 7 ?ree-eigh?s ( an in* 9 diamet]1 & f five-eigh?s to ?ree-qu>t]s ( an in* deep1 & "o in* ap>t1 c5tre to c5tre4 ,a voltage ( ab\t #ae volts 0 employ$4 ,! foll[+ g5]al results 7 arriv$ at3- 7#a7 ,heat+ 9 a p>aff9 ba? always increases ! resi/ance ( wood1 ?\gh only slightly if ! wood be h>d & d5se4 7#b7 ,frequ5t exhau/ion & readmission ( air above ! surface ( ! p>aff9 always has a good effect 9 increas+ ! resi/ance ( wood4 7#c7 ,:5 wood is once dry1 impregnat+ x ) p>aff9 t5ds to keep x dry4 7#d7 ,r$ vulcanis$ fibre1 l wood1 absorbs p>aff91 b x _c be entirely wat]pro($ 9 ?is way4 7#e7 ,! resi/ance ( wood ) /ream l9es along ! gra9 is tw5ty to fifty p] c5t l[] ?an :5 ! /ream l9es cross ! gra94 7#f7 ,! contact resi/ance betwe5 slabs ( wood press$ toge!r is always v high4 ,! foll[+ table w suffici5tly illu/rate ! results obta9$4 ,! /one 0 dri$ 9 ! sun = ?ree weeks 9 ! summ] 7,unit$ ,/ates71 & ! wood is describ$ z hav+ be5 well season$3- ,,curr5t ,,) ,,! ,,gra9 ,l[e/ ,resi/ance ,highe/ ,resi/ance ,l[e/ ,specific ,highe/ ,specific betwe5 two ,cups betwe5 two ,cups ,resi/ance 9 ,resi/ance 9 9 ,megohms4 9 ,megohms4 ,megohms4 ,megohms4 ,a%4 #eej #ibj #chj #gjj ,*]ry #aajj #djjj #bhjj #fjjj ,mahogany #dcj #gcj #caj #faj ,oak #bbj #dbj #ajej #bbjj ,p9e4 #ccj #fcj #cfj #adgj ,h>d p9e4 #aj #dh #ag #ajej ,black walnut #aajj #cjjj #cbj #bajj ,r$ fibre #b #d #c #fj ,slate #ahd #bhj ,soap/one4 #ccj #ejj ,:ite m>ble #bjjj #hhjj #aae4 ,z to work+ ! mat]ials v little ne$ be said4 ,fibre is work$ l wood1 b has ! disadvantage ( rapidly tak+ ! edge (f ! tools4 ,9 turn+ x1 !re=e1 brass-turn+ tools1 ?\gh leav+ n q su* a p]fect f9i% z wood-turn+ tools1 la/ mu* long]1 & really d well en\gh4 ,fibre w n be> heat+ mu* above #ajj;,c--at all ev5ts 9 p>aff94 ,at #adj ,c4 x becomes p]fectly brittle4 ,its *ief m]it lies 9 its great /r5g?4 ,s f> z insulation is conc]n$1 ,mr4 ,peirce's exp]im5ts %[ t x is f> bel[ mo/ k9ds ( wood4 ,slate4 ,?is is a va/ly m useful sub/ance ?an x is g5]ally cr$it$ ) be+4 ,x is v easily work$ at a sl[ spe$1 ei!r on ! %ap+ ma*9e or on ! la!1 ) tools adju/$ = cutt+ brass1 & x keeps its figure1 :i* is m ?an c be said = mo/ mat]ials4 ,x =ms a spl5did base = in/rum5ts1 especially :5 gr\nd ) a little em]y by iron or glass gr9d]s1 f9$ ) its own du/1 & ,fr5* poli%$ 9 ! ord9>y way4 ,spools = coils ( consid]able radial dim5sion may be mo/ conv5i5tly made ( slate in/ead ( wood or brass1 bo? because x keeps its %ape1 & because x insulates suffici5tly well to /op eddy curr5ts--at all ev5ts1 suffici5tly = ord9>y practice4 ,an appreciable advantage is t slate may be pur*as$ at a reasonable rate 9 l>ge slabs ( any desir$ ?ickness4 ,x is g5]ally cut 9 ! laboratory by means ( an old cross-cut saw1 b x does n d mu* damage to a h>d hack saw su* z is us$ = iron or brass4 ,m>ble4 ,accord+ to ,holtzapffell1 m>ble may be easily turn$ by means ( simple po9t$ tools ( good /eel temp]$ to a /raw col\r4 ,! cutt+ po9t is gr\nd on bo? edges l a wood-turn+ tool1 & held up to ! "w at an angle ( tw5ty or ?irty degrees 78) ! horizontal74 ,! m>ble is cut wet to save ! tool4 ,z soon z ! po9t gets1 by gr9d+1 to be ab\t "o-eigh? ( an in* broad x mu/ ei!r be drawn d[n or regr\nd2 a flat tool w n turn m>ble at all4 ,a conv5i5t saw = m>ble is easily made on ! pr9ciple ( ! frame saw4 ,a bit ( hoop iron =ms a conv5i5t blade1 & is %>p5$ by be+ hamm]$ into not*es along "o edge1 us+ ! %>p end ( a hamm] head4 ,! saw is lib]ally suppli$ ) s& & wat]--or em]y & wat]1 :]e economy ( "t is an object4 ,! saw+ ( m>ble is ?us really a gr9d+ process1 b x goes on rapidly4 ,m>ble is gr\nd v easily ) s& & wat]2 x is f9$ ) em]y & poli%$ ) putty p[d]1 :i*1 ,i und]/&1 is be/ us$ ) wat] on clo? or felt4 ,z gr9d+ processes h already be5 fully describ$1 !re is no ne$ to g into !m "h4 ,i h no p]sonal k ( poli%+ m>ble4 #aaf4 ,conductors4 ,! prop]ties ( conductors1 m p>ticul>ly ( metals1 h be5 s frequ5tly exam9$1 t ! lit]ature ( ! subject is appall+ly heavy4 ,9 :at foll[s ,i h endeav\r$ to keep cle> ( :at might prop]ly appe> 9 a treatise on electricity on ! "o h&1 & 9 a wir+ table on ! o!r4 ,! mo/ important "w on ! subject ( ! exp]im5tal resi/ance prop]ties ( metals has be5 done by ,mat?ieson1 ,phil4 ,trans4 #ahfj & #ahfb1 & ,briti% ,association ,reports 7#ahfd72 ,call5d]1 ,phil4 ,trans4 vol4 clxxiii2 ,call5d] & ,griffi?s1 ,phil4 ,trans4 vol4 clxxxii2 ,! ,committee ( ! ,briti% ,association on ,electrical ,/&>ds f #ahfb to ,pres5t ,"t2 ,dew> & ,flem+1 ,phil4 ,mag4 vol4 xxxvi4 7#ahic72 ,klem5cic1 ,wi5] ,sitzungsb]i*te 7,d5ks*rift71 #ahhh1 vol4 xcvii4 p4 #hch2 ,feussn] & ,/4 ,l9deck1 ,zeits*4 fu] ,in/4 ',kunde1 ix4 #ahhi1 p4 #bcc1 & ,b4 ,a4 ,reports1 #ahib1 p4 #aci4 ,( ^!1 ,mat?ieson1 & ,dew> & ,flem+ treat ( resi/ance g5]ally1 ! latt] p>ticul>ly at l[ temp]atures4 ,footnote3 ,! foll[+ is a li/ ( ,dr4 ,mat?ieson's *ief pap]s on ! subject ( ! electrical resi/ance ( metals & alloys3 ,phil4 ,mag4 xvi4 #aheh1 pp4 #bai-bbc2 ,phil4 ,trans4 #aheh1 pp4 #chc-chh ,phil4 ,trans4 #ahfj1 pp4 #afa-agf2 ,phil4 ,trans4 #ahfb1 pp4 #a-bg ,phil4 ,mag4 xxi4 7#ahfa71 pp4 #ajg-aae2 ,phil4 ,mag4 xxiii4 7#ahfb71 pp4 #aga-agi2 ,electrician1 iv4 #ahfc1 pp4 #bhe-bif2 ,briti% ,association ,reports1 #ahfc1 p4 #cea4 ,mat?ieson1 & ,mat?ieson & ,hock91 ,klem5cic1 ,feussn]1 & ,/4 ,l9deck deal ) ! *oice ( metals = resi/ance /&>ds4 ,call5d]'s1 & ,call5d] & ,griffi?s' "w is devot$ to ! /udy ( plat9um = !rmometric purposes4 ,! bibliography ref]r+ to special po9ts w be giv5 lat]4 ,! simple/ way ( exhibit+ ! relative resi/ances ( metals is by means ( a diagram publi%$ by ,dew> & ,flem+ 7loc4 cit471 :i* is reproduc$ on a suitable scale on ! opposite page4 ,= v accurate "w1 9 :i* corrections = ! volumes occupi$ by ! metals at diff]5t temp]atures are ( importance1 ! read] is ref]r$ to ! discussion 9 ! orig9al pap]1 :i* w be f\nd mo/ pleasant read+4 ,f ?is diagram bo? ! specific resi/ance & ! temp]ature coeffici5t may be d$uc$ ) suffici5t accuracy = work%op purposes4 ,9 int]pret+ ! diagram ! foll[+ notes w be ( assi/ance4 ,! diagram is drawn to a scale ( s-call$ plat9um temp]atures--t is to say1 let ,r#j1 ,r#ajj1 ,rt be ! resi/ances ( pure plat9um at #j1 #ajj1 & t ,c4 respectively1 !n ! plat9um temp]ature pt is def9$ z pt #ajj ,x 7,rt-,r#j7_/7,r#ajj-,r#j7 ,?is am\nts to mak+ ! temp]ature scale su* t ! temp]ature at any po9t is proportional to ! resi/ance ( plat9um at t po9t4 ,consequ5tly on a resi/ance temp]ature diagram ! /raight l9e %[+ ! relation betwe5 plat9um resi/ance & plat9um temp]ature w run out at ! plat9um absolute z]o1 :i* co9cides m or less ) ! !rmodynamic absolute z]o1 & also ) ! p]fect gas absolute z]o4 ,plat9um temp]atures may be tak5 = work%op purposes ov] ord9>y ranges z almo/ co9cid+ ) air !rmomet] temp]atures4 ,! metals us$ by ,pr(essors ,dew> & ,flem+ 71 ) "s exceptions1 n absolutely pure1 b 9 g5]al repres5t ! be/ t c be got by ! mo/ ref9$ process ( practical metallurgy4 ,we may note fur!r t ! specific resi/ance is only correct = a temp]ature ( ab\t #ae ,c1 s9ce no correction = ! expansion or contraction ( mat]ial has be5 appli$4 ,! foll[+ notes on alloys suitable = resi/ance coils w probably be f\nd suffici5t4 #aag4 ,plat9oid4 ,?is sub/ance1 discov]$ by ,m>t9o & describ$ by ,bottomley 7,phil4 ,proc4 ,roy4 ,soc4 #ahhe71 is an alloy ( nickel1 z9c1 copp]1 & #a p] c5t to #b p] c5t ( tung/51 b ,i h n be5 able to obta9 an analysis ( its exact composition4 ,x appe>s to be difficult to get ! tung/5 to alloy1 & x has to be add$ to "p ( ! copp] z phosphide ( tung/51 9 consid]ably great] quantity ?an is f9ally requir$4 ,! nickel is add$ to "p ( ! copp] & ! phosphide ( tung/51 !n ! z9c1 & !n ! re/ ( ! copp]4 ,! alloy requires to be remelt$ sev]al times1 & a good deal ( tung/5 is lo/ by oxidation4 ,! alloy is ( a f9e :ite col\r1 & is v little affect$ by air--9 fact1 x is to "s ext5t unt>ni%able4 ,! specific resi/ance w be se5 to be ab\t "o & a half times great] ?an t ( ,g]man silv]1 & ! temp]ature coeffici5t is ab\t #j4jba p] c5t p] degree ,c4 7i4e4 ab\t n9ete5 times less ?an copp]1 & half t ( ,g]man silv]74 ,to all int5ts & purposes x may be reg>d$ z ,g]man silv] ) #a p] c5t to #b p] c5t ( tung/54 ,x does n appe> to h be5 p>ticul>ly exam9$ = secul> *anges ( resi/ance4 #aah4 ,g]man ,silv]4 ,?is mat]ial has be5 exhau/ively exam9$ ( late ye>s by ,klem5cic & by ,feussn] & ,/4 ,l9deck4 ,ev]ybody agrees t ,g]man silv]1 z ord9>ily us$ = resi/ances1 & compos$ ( copp] f\r p>ts1 z9c two p>ts1 nickel "o "p1 is v ill-fitt$ = ! purpose ( mak+ resi/ance /&>ds4 ,?is is due 7#a7 to its exp]i5c+ a consid]able increase 9 resi/ance on w9d+4 ,feussn] & ,/4 ,l9deck f\nd an increase ( #a p] c5t :5 ,g]man silv] 0 w\nd on a core ( t5 wire diamet]s4 7#b7 ,to ! fact t ! *ange goes on1 ?\gh ) gradually decreas+ rate1 = mon?s or ye>s2 7#c7 to ! fact t ! resi/ance is p]man5tly *ang$ 7increas$7 by heat+ to #dj ,c4 or ov]4 ,by artificially age+ coils ( ,g]man silv] by heat+ to #aej ,c1 say = five or six h\rs1 its p]man5cy is greatly improv$1 & x becomes fit = ord9>y resi/ance coils :]e *anges (1 say1 #a_/ejjj d n matt]4 ,x is a rem>kable prop]ty ( all nickel alloys conta9+ z9c t _! specific resi/ance is p]man5tly increas$ by heat+1 :]eas alloys :i* d n conta9 z9c suff] a *ange 9 ! opposite direction4 ,! manufactur]s ( ,g]man silv] appe> to take v little c>e z to ! uni=mity ( ! product put on ! m>ket2 "s s-call$ ,g]man silv] is di/9ctly yell[1 :ile o!r samples are bright & :ite4 ,x is not$ by ,price 7,measurem5ts ( ,electrical ,resi/ance1 p4 #bd7 t ,g]man silv] wire is apt to exhibit great diff]5ces ( resi/ance )9 q %ort l5g?s4 ,?is has be5 my own exp]i5ce z well1 & is a great drawback to ! use ( ,g]man silv] 9 ! laboratory1 = x makes x useless to measure (f def9ite l5g?s ( wire ) a view to obta9+ an approximate resi/ance4 ,9 ,engl& ,g]man silv] coils are g5]ally soak$ 9 melt$ h>d p>aff94 ,9 ,g]many1 at all ev5ts at ! ,*>lott5burg ,in/itute1 accord+ to ,/4 ,l9deck--coils are %ellac-v>ni%$ & bak$4 ,9 any case x appe>s to be ess5tial to ?or\ghly protect ! metal aga9/ atmosph]ic influ5ce4 #aai4 ,plat9um ,silv]4 ,9 ! op9ion ( ,mat?ieson & ( ,klem5cic ! #aj p] c5t silv]1 #ij p] c5t plat9um alloy is ! "o mo/ suitable = resi/ance /&>ds4 ,at all ev5ts1 x has /ood ! te/ ( "t1 =1 ) ! foll[+ exceptions1 all ! ,briti% ,association coils con/ruct$ ( x f #ahfg to ! pres5t day h cont9u$ to agree well toge!r4 ,! exceptions 7 ?ree "o-ohm coils1 :i* p]man5tly increas$ betwe5 #ahhh & #ahij1 probably ?r\gh "s /ra9+ :5 imm]s$ 9 ice4 ,"o coil *ang$ by #j4jjjf 9 #a betwe5 ! ye>s #ahfg & #ahia4 ,accord+ to ,klem5cic1 absolute p]man5cy is n to be expect$ ev5 f ?is alloy4 ,its recomm5dation z a /&>d dep5ds on its *emical in]tness1 its small temp]ature coeffici5t 7#j4jjjbg p] degree71 & its small !rmo-voltage aga9/ copp]1 z ! foll[+ table 7tak5 f ,klem5cic7 w %[3- ,!rmo-voltages 9 ,micro-volts p] degree aga9/ ,copp] ov] ! ,range #j to #ag ,c4 ,plat9um iridium #g4ad micro-volts p] degree ,c4 ,plat9um silv] #f4fb micro-volts p] degree ,c4 ,nickel9 #bh4e micro-volts p] degree ,c4 ,g]man silv] #aj4dc micro-volts p] degree ,c4 ,mangan9 7,/4 ,l9deck7 #a4e micro-volts p] degree ,c4 ,me*anically1 ! plat9um silv] is weak1 & is greatly affect$ z to its resi/ance by me*anical /ra9s--9 fact1 ,klem5cic consid]s x ! wor/ sub/ance he exam9$ f ?is po9t ( view--a conclusion r borne out by ,mr4 ,glazebrook's exp]i5ce ) ! ,briti% ,association /&>ds already ref]r$ to 7,b4 ,a4 ,reports1 #ahia & #ahib74 ,tak+ ev]y?+ into acc\nt1 x w probably be well to con/ruct /&>ds ei!r ) oil insulation only1 or to bake ! coils 9 %ellac be=e te/+1 in/ead ( soak+ 9 p>aff94 ,fig4 #hi illu/rates a =m ( an oil imm]s$ /&>d :i* is 9 use 9 my laboratory1 & ?r\gh :i* a consid]able curr5t may be pass$4 ,! oil is /irr$ by means ( a screw propell]4 ,fig4 #hi4 ,fig4 #hi repres5ts a /&>d resi/ance = mak+ ,cl]k cell comp>isons by ! silv] voltamet] me?od4 ,! framework on :i* ! coils are w\nd consi/s ( a base & top ( slate4 ,! pill>s are ( fl9t glass tube surr\nd+ brass bolts1 & cem5t$ to ! latt] by raw %ellac4 ,grooves are cut 9 ! glass sleeves to hold ! wires well ap>t4 ,^! grooves 7 cut by means ( a file work+ ) k]os5e lubrication4 ,a screw /irr] is provid$1 & ! :ole app>atus is imm]s$ 9 k]os5e 9 ! glass box ( a /orage cell4 ,! app>atus is ag$ to beg9 ) by heat+ to a temp]ature a good deal high] ?an any temp]ature x is expect$ to rea* 9 actual "w4 ,aft] ?is ! rigidity ( ! frame is int5d$ to prev5t any fur!r /ra9+ ( ! wire4 ,! app>atus z figur$ is n int5d$ to be cool$ to #j ,c1 s t x is put 9 z l>ge a box z possible to ga9 ! advantage ( hav+ a l>ge volume ( liquid4 ,! top & bottom slates measure sev5 in*es by sev5 in*es1 & ! di/ance betwe5 !m is sev5 in*es4 ,! inn] coil is w\nd on fir/1 & ! loop :i* con/itutes ! end ( ! w9d+ is br\ght up to a suitable position = adju/m5t4 ,! insulation ( ! heavy copp] connectors is by means ( ebonite4 #abj4 ,plat9um ,iridium4 ,plat9um #ij p] c5t1 iridium #aj p] c5t4 ,?is mat]ial 0 prep>$ 9 "s quantity at ! co/ ( ! ,fr5* ,gov]nm5t1 & di/ribut$ = te/ ab\t #ahhf4 ,klem5cic got "s ( x z repres5t+ ,au/ria1 & f\nd x behav$ v l ! plat9um silv] alloy j discuss$4 ,! temp]ature coeffici5t is1 h[ev]1 high] ?an = plat9um silv] 7#j4jjabf z aga9/ #j4jjjbg74 ,! me*anical prop]ties ( ! alloy are1 h[ev]1 mu* bett] ?an ^? ( ! silv] alloy2 & 9 view ( ! exp]i5ce ) ,b4 ,a4 /&>ds above quot$1 x rema9s an op5 "q :e!r1 on ! :ole1 x w\ld n be ! bett] mat]ial = /&>ds1 9 spite ( its high] price4 ,improvem5ts 9 absolute measurem5ts ( resi/ance1 h[ev]1 may r5d] prim>y /&>ds sup]flu\s4 #aba4 ,mangan94 ,discov]$ by ,we/on--at all ev5ts z to its application to resi/ance coils4 ,a glance at ! diagram w exhibit its unique prop]ties1 on acc\nt ( :i* x has be5 adopt$ by ! ,physikalis* ,te*nis*5 ,rei*san/alt = resi/ance /&>ds4 ,! composition ( ! alloy is copp] #hd p] c5t1 manganese #ab p] c5t1 nickel #d p] c5t1 & x is describ$ z ( a /eel-gray col\r4 ,un=tunately x is apt to oxidise 9 ! air1 or r ! manganese x conta9s does s1 s t x wants a v p]fect protection aga9/ ! atmosph]e4 ,l ,g]man silv]1 mangan9 *anges 9 resi/ance on w9d+1 & coils made ( x require to be artificially ag$ by heat+ to #aej = five h\rs be=e f9al adju/m5t4 ,! anneal+ _c be c>ri$ out 9 air1 ow+ to ! t5d5cy to oxidation4 ,! me?od adopt$ by ,/4 ,l9deck 7at all ev5ts up to #ahib7 is to treat ! coil ) ?ick alcoholic %ellac v>ni% till ! insulation is ?or\ghly saturat$1 & !n to bake ! coil z describ$4 ,! bak+ n only anneals ! wire1 b r$uces ! %ellac to a h>d & highly insulat+ mass4 ,:e!r /resses ( suffici5t magnitude to produce s]i\s me*anical effects c be set up by unequal expansion ( wire & %ellac dur+ heat+ & cool+ is n yet kn[n1 b s f> z te/$ 7& x mu/ be presum$ t ! ,rei*san/alt te/s are ?or\gh7 no difficulty seems to h be5 met )4 ,9 c\rse ( "t1 h[ev]1 probably ! be/ %ellac coat+ w crack1 & !n adieu to ! p]man5cy ( ! coil6 ,?is might1 ( c\rse1 be obviat$ by keep+ ! coil 9 k]os5e1 :i* has no action on %ellac1 b :i* decomposes some:at itself4 ,! me?od ( treatm5t above describ$ suffices to r5d] coils ( mangan9 con/ant = at lea/ a ye> 79 #ahib ! te/s _h only be5 made = ?is "t7 )9 a few ?\s&s p] c5t4 ,mangan9 c be obta9$ 9 %eets1 & f ?is mat]ial /&>ds ( #aj-b1 #aj-c1 & #aj-d ohms are made by sold]+ /rips betwe5 /\t copp] b>s1 & ^! are adju/$ by gradually increas+ _! resi/ance by bor+ small holes ?r\gh !m4 ,! sold] employ$ is said to be silv]4 ,mr4 ,griffi?s 7,phil4 ,trans4 vol4 clxxxiv4 #ahic1 ,a1 p4 #cij7 has _h "s exp]i5ce ) mangan9 c>ry+ comp>atively heavy curr5ts1 "u :i* circum/ances its resi/ance :5 imm]s$ 9 wat] 0 f\nd to rise 9 spite ( ! v>ni% :i* coat$ x4 ,o!r exp]im5ts 9 :i* ! mangan9 wire 0 imm]s$ 9 p>aff9 oil did n exhibit ?is effect1 ?\gh /rong] curr5ts 7 pass$4 ,on ! :ole1 mangan9 appe>s to be ! be/ mat]ial = coil boxes & second>y resi/ance /&>ds4 ,:e!r x is fit to rank ) ! plat9um alloys z reg>ds p]man5cy mu/ be treat$ z an op5 "q4 #abb4 ,o!r ,alloys4 ,! foll[+ tables1 tak5 f ! "w ( ,feussn] & ,/4 ,l9deck1 ,zeits*rift fu] ,in/rum5t5 ,kunde1 #ahhi1 vol4 ix4 p4 #bcc1 toge!r ) ! foll[+ notes1 w suffice4 #abc4 ,nickel94 ,?is is only ,g]man silv] ) a little less z9c1 a little m nickel1 & traces ( cobalt & manganese4 ,x behaves l ,g]man silv]1 b is an improvem5t on ! latt] 9 t all ! faults ( ,g]man silv] appe> ^u a r$uc$ scale 9 nickel94 #abd4 ,pat5t ,nickel4 ,practically a copp] nickel alloy1 us$ to "s ext5t by ,siem5s & ,halske4 ,x /&s pretty well 9 ! same relation to nickel9 z ! latt] does to ,g]man silv]4 ,aft] anneal+ z = mangan9 x c be made into s]viceable /&>ds :i* d n *ange m ?an a few ?\s&?s p] c5t4 ,i h n come across a /atem5t ( its !rmo-voltage aga9/ copp]4 #abe4 ,con/ant94 ,ano!r nickel copp] alloy conta9+ #ej p] c5t ( ea* con/itu5t4 ,x appe>s to be a s]viceable sub/ance1 hav+ a temp]ature coeffici5t ( #j4jjc p] c5t p] degree only1 b an exce$+ly high !rmo-voltage1 viz4 #dj micro-volts p] degree aga9/ copp]4 #a #b #c #d #e #f #g #h ,g]man ,nickel9 made ,rheo- ,pat5t ,nickel ,manga- ,nickel ,silv] by ,ob]mai] tane nese ,manga- ,dia- ,dia- ,dia- ,dia- ,copp] nese met] met] met] met] ,copp] #a4jmm #j4amm #j4fmm #a4jmm ,copp] #fj4af #fa4fc #ed4eg #ec4bh #gd4da #gd4ga #gj #gc ,z9c #be4cg #ai4fg #bj4dd #af4hi #j4bc #j4eb 444 444 ,t9 444 444 444 444 trace 444 444 ,nickel #ad4jc #ah4df #bd4dh #be4ca #be4aj #bd4ad 444 #c ,iron #j4cj #j4bd #j4fd #d4df #j4db #j4gj 444 444 ,cobalt trace #j4ai 444 444 trace trace 444 444 ,mang- trace #j4ah #j4bg #j4cg #j4ac #j4ag #cj #bd anese4 #ii4hf #ajj4cg #ajj4dj #ajj4ca #ajj4bd #ajj4bd 444 444 ,specific resi/ance #cj4j #cc4b #dd4h #eb4e #cd4b #cb4h #ajj4f #dg4g ,temp]ature coeffici5t #j4jjjcf #j4jjjcj #j4jjjcc #j4jjjda #j4jjjai #j4jjjba #j4jjjjd #j4jjjjc ,! specific resi/ance is 9 microhms1 i4e4 #aj-f ohms p] cubic c5timetre1 & ! temp]ature coeffici5t 9 degrees c5tigrade4 #abf4 ,nickel ,manganese ,copp]4 ,i c f9d no o!r ref]5ce ) reg>d to ?is alloy m5tion$ by ,l9deck4 ,ni*olls1 h[ev] 7,silliman's ,j\rnal #c1 #ci1 #aga1 #ahij71 gives "s p>ticul>s ( alloys ( copp] & f]romanganese4 ,! foll[+ table is tak5 f ,wi$emann's ,beiblatt] 7ab/ract ( ,ni*oll's pap]1 #ahij1 p4 #haa74 ,all ^! alloys appe> to require anneal+ at a r$ heat be=e _! resi/ances are any?+ l con/ant4 ,let x be p]c5tage ( copp]1 !n #ajj--x is p]c5tage ( f]romanganese4 ,values ( x4 #ajj #ii4bf #ia 4#hh #hf4ih #hj4d #gj4fe ,specific resi/ance ) respect to copp] 78 pure7 #a #a4ai #aa4bh #bj4d #bg4e #de4a ,temp]ature coeffici5t p] degree x #ajf7;h>d7 #cbjb #bafg #ach #af #bb -#bd ,ditto 7s(t7 444 444 #ahd #hj #ff #ba ,if nickel is add$1 alloys ( mu* ! same "* are obta9$1 "s ) negative temp]ature coeffici5ts--= in/ance1 "o conta9+ #eb4ea p] c5t copp]1 #ca4bg p] c5t f]romanganese1 & #af4bb nickel4 ,a detail$ acc\nt ( sev]al alloys w be f\nd 9 a pap] by ,griffi?s 7,phil4 ,trans4 #ahid1 p4 #cij71 b z ! con/ants 7 det]m9$ to a high] ord] ( accuracy ?an ! composition ( ! mat]ial--or1 at all ev5ts1 to a high] degree ( accuracy ?an t to :i* ! mat]ials c be reproduc$--!re is no advantage 9 quot+ !m "h4 ,,*apt] ,,iv ,,electroplat+ ,,& ,,alli$ ,,arts #abg4 ,electroplat+4 ,?is is an art :i* is usually deem$ wor?y ( a treatise to itself1 b = ord9>y laboratory purposes x is a v simple matt]--s simple1 inde$1 t ! multiplicity ( receipts z giv5 9 treatises are r a s\rce ( emb>rassm5t ?an o!rwise4 ,! fundam5tal pr9ciples ( ! art are3- 7#a7 ,dirty "w _c be electroplat$4 7#b7 ,electroplat$ surfaces may be r\gh]1 b w n be smoo!r ?an ! orig9al unplat$ surface4 7#c7 ,! art ( electroplat+ be+ 9 advance ( ! sci5ce1 x is necess>y to be c>eful z to c>ry+ out in/ructions 9 detail4 ,?is p>ticul>ly applies to ! conditions :i* det]m9e :e!r a metallic deposit %all come d[n 9 a regul9e or 9 a cry/all9e mann]4 #abh4 ,! ,dipp+ ,ba?4 ,an acid dipp+ ba? is "o ( ! mo/ useful adjuncts to ! laboratory1 n only = cleans+ metals = electroplat+1 b = clean+ up app>atus made out ( bits ( brass tube & %eet1 & p>ticul>ly = quickly clean+ b9d+ screws1 etc1 :]e x is necess>y to ensure good electrical contact4 ,! *eape/ & mo/ satisfactory way 9 ! end is to make up two or ?ree r l>ge ba?s to beg9 )4 ,! glass boxes ( /orage batt]ies d v nicely = ! purpose1 & be+ g5]ally gr\nd pretty flat at ! top1 !y may be cov]$ by %eets ( pat5t plate glass1 & ?us pres]v$ f ! action ( ! air4 ,fir/ ,ba?4 ,a #cj or #dj p] c5t solution ( comm]cial cau/ic soda4 ,objects may be cleans$ f grease 9 ?is ba? by heat+ !m z hot z is consi/5t ) individual circum/ances1 & plung+ !m into x4 ,x is a consid]able advantage to beg9 by remov+ grease f articles subsequ5tly to be dipp$ 9 an acid ba?1 bo? because x saves "t & acid1 & because m uni=m results are obta9able :5 ?is is done ?an :5 x is omitt$4 ,x is a great advantage to h ! cau/ic soda solution hot4 ,?is is always done 9 factories :]e nickel-plat+ is c>ri$ on1 b x is inconv5i5t 9 ! laboratory4 ,! articles aft] dipp+ 9 ! alkali are swill$ ) wat]1 & may ev5 be scrubb$ ) a bru%1 s z to remove greasy matt]s t h be5 s(t5$ b n entirely remov$4 ,acid ,ba?4 ,a conv5i5t ba? = laboratory purposes is made by mix+ two volumes ( /rong comm]cial nitric acid ) "o ( /rong sulphuric acid 9 a cell measur+1 say1 #ab ,x #aj ,x #ae in*es4 ,copp] or brass articles are dipp$ 9 ?is ba? = a few seconds1 !n r9s$ ) wat]1 !n dipp$ aga9 = a second or two1 or until !y appe> equally :ite all ov]1 & !n )drawn z rapidly z possible & plung$ into a l>ge quantity ( clean wat]4 ,c>e mu/ be tak5 to transf] ! articles f ! ba? to ! wat] z quickly z possible1 = if "t be all[$ = gas to be evolv$1 ! surfaces become mat in/ead ( bright4 ,9 ord] to save acid x is advisable to make up a ?ird ba?1 us+ ^? odds & ends ( acids :i* gradually accumulate 9 ! laboratory4 ,sulphuric acid f ! balance cases1 = in/ance1 mix$ ) its own volume ( comm]cial nitric acid1 does v well4 ,! objects to be dipp$ receive a prelim9>y cleans+ by a dip 9 ?is ba?1 ! /rong ba? be+ res]v$ = ! f9al dip4 ,%eet brass & drawn tube1 z x comes f ! mak]s1 possesses a really f9e surface1 ?\gh ?is is g5]ally obscur$ by grease & oxide4 ,"w execut$ 9 ^! mat]ials1 clean$ 9 alkali1 & dipp$ 9 really /rong acid1 w be f\nd to pres5t a mu* bett] appe>ance ?an "w :i* has be5 fil$1 unless ! latt] be aft]w>ds elaborately poli%$4 ,on no acc\nt mu/ p>aff9 be all[$ to get into any ( ! ba?s4 ,:5 ! f9al ba? gets weak x mu/ be relegat$ to a subord9ate position & a new ba? set up4 ,a weak acid ba? leaves an ugly mottl$ surface on brass "w4 #abi4 ,a metallic surface :i* x is int5d$ to electroplate mu/1 z has be5 m5tion$1 be scrupul\sly clean4 ,if ! metal is n too valuable or delicate1 clean+ by dipp+ is easy & effectual4 ,! foll[+ notes w be f\nd to apply to special cases :i* (t5 occur4 7#a7 ,silv] ,surfaces int5d$ to be gilt4 ,^! are fir/ wa%$ clean ) soap & hot wat]1 & poli%$ ) :it5+4 ,!y are !n dipp$ = a mom5t 9 a boil+ solution ( potassium cyanide4 ,a #bj p] c5t solution ( common comm]cial cyanide does well1 b ! exact /r5g? is q immat]ial4 ,! cyanide is wa%$ away 9 a l>ge volume ( s(t wat]1 & ! articles are kept "u wat] till !y are scrat*-bru%$4 ,mat surfaces are readily produc$ on /&>d silv] by dipp+ 9 hot /rong sulphuric acid4 ,! appe>ance ( new silv] co9s1 :i* is famili> to ev]ybody1 is obta9$ by ?is process4 7#b7 ,f9ely turn$ & f9i%$ ,brass ,"w4 ,if x is int5d$ to nickel-plate su* "w1 & if x is desirable to obta9 brightly poli%$ nickel surfaces1 ! "w mu/ be p]fectly poli%$ to beg9 )4 ,full details z to poli%+ may be f\nd 9 work%op books or treatises on wat*-mak+4 ,x w suffice "h to say t ! brass "w is fir/ smoo!d by ! application ( successive grades ( em]y & oil1 or by v f9e dead smoo? files cov]$ ) *alk4 ,poli%+ is c>ri$ out by means ( rott5 /one & oil appli$ on lea!r4 ,9 poli%+ turn$ "w c>e mu/ be tak5 to move ! file1 em]y1 or rott5 /one to & fro ov] ! "w ) great regul>ity1 or ! surface w end by look+ scrat*y & irregul>4 ,! fir/ process ( clean+ is1 ( c\rse1 to remove grease1 & ?is is accompli%$ be/ by dipp+ 9 a ba? ( /rong hot cau/ic soda solution1 & less p]fectly by heat+ ! "w & dipp+ x 9 ! cold cau/ic soda ba?4 ,dur+ ?is process a c]ta9 am\nt ( *emical action (t5 occurs lead+ to ! brass surface exhibit+ "s discoloration4 ,! be/ way ( rem$y+ ?is is to dip ! brass into a hot ba? ( cyanide ( potassium solution4 ,if x is inconv5i5t to employ hot ba?s or to heat ! brass "w1 good results may be obta9$ by rubb+ ! articles ov] ) a l>ge r\gh cork pl5tifully lubricat$ ) a /rong solution ( an alkali4 ,if ! surfaces are v soil$ or dirty1 a pa/e ( alkali & f9e slak$ lime may be appli$ on a cork rubb]1 & ?is 9 my exp]i5ce has always be5 mo/ effective & satisfactory 9 e way1 except t x is difficult to get into crevices4 ,if ! alkali /a9s ! "w1 a little cyanide ( potassium may be rubb$ ov] ! surface 9 a simil> mann]4 ,brass "w treat$ by ei!r ( ^! me?ods is to be wa%$ 9 clean wat] till ! alkali is entirely remov$1 & may !n be nickel-plat$ )\t any prelim9>y scrat*-bru%+4 ,! treatm5t 9 hot ba?s ( alkali & cyanide is ! me?od g5]ally employ$ 9 ,am]ican factories z a prelim9>y to ! nickell+ ( small brass "w = sew+ ma*9es1 etc4 7#c7 ,copp] ei!r = use z ! ka?ode 9 electrolysis calibration exp]im5ts or o!rwise is mo/ conv5i5tly prep>$ by dipp+ 9 ! acid ba?1 r9s+ quickly 9 cold wat]1 scrat*-bru%+ "u cold wat]1 & transf]r+ at once to ! plat+ ba?4 ,9 ! case :]e ! copp] plates require to be weigh$ !y are dipp$ into v hot di/ill$ wat] aft] scrat*-bru%+1 & !n dri$ at once by means ( a clean glass clo?4 7#d7 ,alum9ium 7:i*1 h[ev]1 does n readily l5d itself to plat+ op]ations ,footnote3 ,?is difficulty has n[ be5 ov]come4 ,see note1 section #ach4 7 is be/ treat$ by alkali rubb$ on ) a cork1 or by a hot alkal9e c>bonate :]e rubb+ is inexp$i5t4 ,! clean alum9ium is scrat*-bru%$ "u wat]1 & at once transf]r$ to ! plat+ ba?4 7#e7 ,iron = ,nickel-plat+4 ,accord+ to ,dr4 ,gore 7,electra-metallurgy1 p4 #cai7 ! be/ ba? = clean+ iron is made z foll[s3 ,"o gallon ( wat] & "o p\nd ( sulphuric acid are mix$ ) "o or two ounces ( z9c 7:i* ( c\rse dissolves72 to ?is is add$ half a p\nd ( nitric acid4 ,! writ] has be5 accu/om$ to clean iron by me*anical means1 to deprive x ( grease by cau/ic alkali1 & to f9i% x (f by1 means ( a h>d scrat* bru%4 ,?is process has always work$ satisfactorily4 7#f7 ,articles sold]$ ) s(t sold] conta9+ lead & t9 d n readily l5d !mselves to electrolytic processes1 ! sold] g5]ally becom+ black & refus+ to be coat$ ) ! electro-deposit4 ,moreov]1 if sold]$ articles are boil$ = any l5g? ( "t 9 cau/ic alkali dur+ ! prelim9>y cleans+1 en\gh t9 w dissolve to =m a solution ( /annate ( pota% or soda--/rong en\gh to deposit t9 on brass or copp]4 ,a me?od ( copp]+ sold]$ articles w be describ$ lat] on4 #acj4 ,scrat*-bru%+4 ,?is process is g5]ally indisp5sable1 & to its omission is to be trac$ mo/ laboratory failures 9 electroplat+4 ,scrat*-bru%es may be b\ght at ^? int]e/+ %ops :]e wat*mak]s' supplies are sold4 ,x w be well1 !re=e1 to pur*ase a selection ( scrat* bru%es1 = !y are made to suit p>ticul> k9ds ( "w4 ,!y are all made ( brass wire1 & v>y bo? 9 h>dness & 9 ! f95ess ( ! wire4 ,! simple/ k9d ( scrat* bru% consi/s m]ely ( a bundle ( wires b\nd up tightly by ano!r wire1 & some:at frizz$ out at ! ends 7,fig4 #ij74 ,a m useful k9d is made j l a rotat+ bru%1 & has to be m\nt$ on a la! 7,fig4 #ia74 ,fig4 #ij4 ,fig4 #ia4 ,! scrat* bru% is g5]ally1 if n always1 appli$ wet2 ! lubricant g5]ally recomm5d$ is /ale be]1 b ?is may be replac$ by wat] conta9+ a small quantity ( glue1 or any o!r =m ( gelat9e 9 solution--a m]e trace 7say 4#a p] c5t7 is q suffici5t4 ,v fair results may be got by us+ ei!r pure or soapy wat]4 ,! rotat+ bru%es require to be m\nt$ on a la!1 & may be run at ! same spe$ z w\ld be employ$ = turn+ wood5 objects ( ! same dim5sions4 ,s9ce ! bru% has to be kept wet by all[+ wat] or its equival5t to drip ^u x1 x is usual to make a t9 tr\gh ov] :i* ! bru% c revolve1 & to fur!r protect ?is by a t9 hood to keep ! liquid f be+ ?r[n all ov] ! room4 ,9 _m works ! bru% is arrang$ to lie p>tly 9 ! liquid1 & ?is does v well if ! hood is effective4 ,!re is a sup]/ition t electro-deposits /ick bett] to scrat*-bru%$ surfaces ?an to surfaces :i* h n be5 s treat$1 & consequ5tly x is usual to scrat*-bru% surfaces be=e electro-deposit4 ,h[ev] ?is may be1 !re is no d\bt t adh]5ce & solidity are promot$ by frequ5t scrat*-bru%+ dur+ ! process ( deposit+ metal1 especially :5 ! latt] t5ds to come d[n 9 a spongy mann]4 ,gilt surfaces--if ! gild+ is at all heavy--are g5]ally dull yell[1 or ev5 br[n1 :5 !y come f ! ba?1 & require ! scrat* bru% to cause ! gold to bright51 an (fice :i* x p]=ms 9 a q /rik+ mann]4 ,! same rem>k applies to silv]$ surfaces1 :i* g5]ally leave ! ba? a dead :ite--at all ev5ts if ! deposit is ?ick1 & if ord9>y solutions are employ$4 ,9 ei!r case ! t\* ( ! scrat* bru% is magical4 #aca4 ,burni%+4 ,burni%]s ( /eel1 agate1 or blood/one c be b\ght at ! %ops :]e scrat* bru%es are sold1 & are us$ to produce ! same bright5+ effect z c be got by scrat*-bru%+4 ,! same solutions are employ$1 b r /rong]1 & ! burni%] is swept ov] ! surface s z to compress ! deposit$ metal4 ,burni%+ is r an art1 b :5 well done gives a h>d] & m brilliant 7because smoo!r7 surface ?an ! scrat* bru%4 ,on ! :ole1 /eel burni%]s are ! mo/ conv5i5t if 9 con/ant use4 ,if ! burni%+ tools h to lie ab\t1 /eel is apt to ru/1 unless c>efully protect$ by be+ plung$ 9 quicklime or ?ickly sme>$ ) vasel9e1 & ! lea/ speck ( ru/ is fatal to a burni%]4 ,9 any case ! /eel requires to be occasionally repoli%$ by r\ge & wat] on a bit ( clo? or felt4 ,! process ( burni%+ is necess>ily some:at sl[ & t$i\s1 & z a rule is n wor? tr\bl+ ab\t except 9 cases :]e great p]man5ce is requir$4 ,! burni%] is mov$ ov] ! "w some:at l a p5cil ) consid]able pressure1 & c>e is tak5 to make ! /rokes z uni=m 9 direction z possible2 o!rwise ! surface looks non-uni=m1 & has to be fur!r poli%$ by tripoli1 :it5+1 etc1 be=e x is pres5table4 #acb4 ,silv]-plat+4 ,! mo/ conv5i5t solution = g5]al purposes is an #h to #aj p] c5t solution ( ! d\ble cyanide ( silv] & potassium toge!r ) #a or #b p] c5t ( free potassium cyanide4 ,great latitude is p]missible 9 ! /r5g? ( solution & d5sity ( curr5t4 ,z comm]cial cyanide ( potassium g5]ally conta9s an unkn[n p]c5tage ( o!r salts1 :i*1 h[ev]1 d n int]f]e ) its value = ! purpose ( silv]-plat+1 ! simple/ proc$ure is z foll[s4 ,= e #ajj c4c4 ( plat+ solution ab\t #g grms4 ( dry cry/allis$ silv] nitrate are requir$4 ,! equival5t am\nt ( potassium cyanide 7if dry & pure7 is #e4b grms1 b comm]cial cyanide may conta9 f #ej p] c5t upw>ds to #if p] c5t 9 ! be/ fus$ cyanide made f f]rocyanide only4 ,an approximate idea ( ! cyanide cont5t c be obta9$ f ! deal]s :5 ! salt is pur*as$1 & ?is is all t is requir$4 ,a quantity slightly 9 excess ( ! comput$ am\nt ( cyanide is dissolv$ 9 di/ill$ wat]1 & ?is is cauti\sly add$ to ! solution ( ! silv] nitrate till precipitation is j complete4 ,! sup]natant liquors are !n dra9$ away1 & ! precipitate dissolv$ by add+ a suffici5cy ( ! rema9+ cyanide2 ?is process is assi/$ by w>m+ & /irr+4 ,an all[ance ( ab\t "o-t5? ( ! :ole cyanide employ$ may be add$ to =m free cyanide1 & ! solution made up to ! /r5g? nam$4 ,x is advisable to beg9 ) ! cyanide 9 a mod]ately /rong solution1 = ! sake ( ease 9 dissolv+ ! precipitate4 ,?is solution w deposit silv] ^u articles ( copp] or brass imm]s$ 9 x ev5 )\t ! batt]y1 b ! coat w be ?94 ,! solution is us$ cold1 ) a curr5t d5sity ( ab\t #aj to #bj ampres p] squ>e foot4 ,! articles to be silv]$ are scrat*-bru%$1 wa%$1 & electroplat$1 till !y beg9 to look undesirably r\gh4 ,!y are !n tak5 out ( ! ba?1 rebru%$1 & ! process cont9u$ till a suffici5cy ( silv] is deposit$4 ,f\r grammes weight ( silv] 7ne>ly7 is deposit$ p] ampre h\r4 ,x is be/ to use a f9e silv] anode1 s t ! solution1 does n get contam9at$ by copp]4 ,9 mo/ factories x is usual to quick5 ! objects to be silv]$ be=e plac+ !m 9 ! electrolysis vats1 because ! deposit is said to adh]e bett] 9 consequ5ce ( ?is treatm5t4 ,i h nev] f\nd x any improvem5t = laboratory purposes1 b x is easy to d4 ,a dilute 7say #b p] c5t7 solution ( cyanide ( m]cury is requir$ conta9+ a little free cyanide4 ,! objects to be quick5$ are scrat*-bru%$ & dipp$ into ! cyanide ( m]cury solution till !y are uni=mly :ite2 x is g5]ally agre$ t ! less ! m]cury deposit$ ! bett]1 s long z a p]fect coat+ is obta9$4 ,! objects are r9s$ aft] quick5+1 & put 9 ! deposit+ ba? at once4 ,! mat surface ( silv] obta9$ by electrolysis ( ! cyanide is v beautiful--"o ( ! mo/ beautiful ?+s 9 nature--%9+ ) incomp>able cry/all9e :it5ess4 ,s delicate is x1 h[ev]1 = s great is ! surface x exposes1 t x is g5]ally rapidly det]iorat$ by exposure to ! air4 ,x may be protect$ to "s ext5t by lacqu]+ ) pale lacqu]1 b x loses "s ( its brilliancy & purity 9 ! process4 ,! deposit is g5]ally scrat*-bru%$ or burni%$ d[n to a regul> reflect+ surface4 #acc4 ,cold ,silv]+4 ,a ?9 b brilliant coat ( silv] may be readily appli$ to small articles ( brass or copp] 9 ! foll[+ way4 ,a saturat$ solution ( sodium sulphite 7neutral7 is prep>$1 & into ?is a #aj p] c5t solution ( nitrate ( silv] is p\r$ s long z ! precipitate =m$ is r$issolv$4 ,a good deal ( silv] may be got into solution 9 ?is way4 ,articles to be silv]$ ne$ only to be clean$1 bru%$1 & dipp$ 9 ?is solution till a coat ( ! requir$ ?ickness is obta9$4 ,i mu/ admit1 h[ev]1 t ! coat+ ?us laid on does n appe> to be s p]man5t z "o deposit$ by simple imm]sion f ! cyanide solution1 ev5 ?\gh x is ?ick]4 ,! cyanide plat+ solution w itself give a good coat ( silv] if x is us$ boil+1 & if a little potassium cyanide be add$4 ,= purposes ( in/rum5t con/ruction1 h[ev]1 a ?9 coat ( silv] is seldom to be recomm5d$1 on acc\nt ( its liability to t>ni% & its rapid de/ruction :5 any attempt is made to repoli% x4 ,= ^! reasons1 nickel or gold plat+ is mu* to be pref]r$4 #acd4 ,gild+4 ,?is art des]ves to be mu* m widely practis$ ?an is usual 9 laboratories4 ,reg>d$ z a means ( pres]v+ brass1 copp]1 or /eel1 x is n appreciably m "t robb+ ?an lacqu]+1 & gives inf9itely bett] results4 ,moreov]1 x is n mu* m exp5sive4 ,/range z x may seem1 ! co/l9ess ( gild+ seldom lies 9 ! value ( ! gold deposit$2 ! *ief co/ is 9 ! *emicals employ$ to clean ! "w1 & 9 int]e/ on ! n inconsid]able outlay on ! solution & anode4 ,! easie/ metal to gild is silv]1 & x is n unusual to give base metals a ?9 coat+ ( silv] or copp]1 or bo?1 "o aft] ! o!r1 be=e gild+1 9 ord] to secure uni=mity4 ,to illu/rate ! virtue ( a ?9 lay] ( gold1 ,i w m5tion ! foll[+ exp]im5t4 ,ab\t ?ree ye>s ago ,i le>n$ = ! fir/ "t t to clean ! silv] us$ 9 a small h\sehold requir$ at lea/ an h\r's lab\r p] diem4 ,i fur!r asc]ta9$ t mo/ ( ?is "t is sp5t on ! poli%+ "p ( ! process4 ,z ?is seem$ a wa/e ( lab\r1 ,i decid$ to try ! effect ( gild+4 ,9 ord] to give ! proposal a fair trial ,i gilt ! foll[+ articles3 half a doz5 table spoons & =ks1 a doz5 dess]t =ks & spoons1 & a doz5 tea spoons4 ,^! 7 all common electroplat$ w>e4 ,!y 7 weigh$ be=e & aft] gild+1 & x 0 ) difficulty t ! increase ( weight 0 detect$1 ev5 ?\gh a f9e bullion balance 0 employ$4 ,on calculat+ back to money1 x appe>$ t ! value ( ! gold deposit$ 0 ab\t ?reep5ce4 ,assum+ t an equal weight ( silv] _h be5 accid5tally dissolv$ by ! free cyanide dur+ ! plat+--:i* is unlikely--! total am\nt ( gold deposit$ w\ld be wor?1 say1 sixp5ce4 ,aft] ?ree ye>s' cont9u\s use ! gild+ is /ill p]fect1 except at ! po9ts on :i* ! spoons & =ks re/1 :]e x is c]ta9ly r %abby4 ,mean:ile ! gold plate only requires to be wa%$ ) hot wat] & soap to keep x 9 p]fect ord]1 a mu* m cleanly & exp$iti\s process ?an t ( silv] clean+4 #ace4 ,prep>+ ,surfaces = ,gild+4 ,ord9>y brass "w--r\gh or smoo?--may = purposes ( pres]vation be dipp$1 scrat*-bru%$1 & gilt at once4 ,sev5 ye>s ago ! writ] gilt ! inside ( ! head ( a copp] wat] /ill1 & simply scrat*-bru%$ x2 x is to-day 9 z good ord] z :5 x 0 fir/ done4 ,if x is int5d$ to gild "w f ! fir/1 ) ! view ( mak+ an exceptionally f9e job ( x1 gild+ metal1 i4e4 brass conta9+ "o to "o & a qu>t] ounces ( z9c to ! p\nd ( copp] may be specifi$4 ,f its co/l9ess1 h[ev]1 ?is is only desirable = small "w4 ,iron & /eel are g5]ally giv5 a prelim9>y coat+ ( copp]1 b ?is may be disp5s$ ) ?\gh ) no advantage--by us+ a p>ticul> process ( gild+4 ,base metals1 z9c1 pewt]1 lead1 etc1 are fir/ copp]$ 9 a cyanide ( copp] solution1 z w be describ$ "u ! head ( ,copp]-plat+4 ,if x is int5d$ to gild sold]$ articles1 ! prelim9>y coat+ ( copp] is ess5tial4 ,! mo/ conv5i5t vessel = hold+ a gild+ solution is und\bt$ly "o =m$ ( enamell$ iron4 ,p>ticul>ly useful are ! buckets & billies 7i4e4 cyl9drical cans7 made ( ?is mat]ial4 ,^! vessels may be heat$ )\t any fe> ( a sma%1 & d n appe> to be appreciably affect$ by gild+ solutions--at all ev5ts dur+ sev]al days or weeks4 ,! avoidance ( all risk ( breakage :5 tw5ty or ?irty p\nds' wor? ( solution is 9 "q is a matt] ( importance4 ,"u no circum/ances is x desirable to use any?+ b ! pure/ gold & be/ fus$ cyanide 7call$ gold cyanide7 9 ! prep>ation ( ! solutions4 ,! appe>ance ( a pure gold deposit is f> ri*] ?an ( "o conta9+ silv]1 & its resi/ance to ! atmosph]e is p]fect2 moreov]1 9 *emico-physical processes "o has ! satisfaction ( kn[+ :at "o is deal+ )4 #acf4 ,gild+ ,solutions4 ,! /r5g? ( solution necess>y = gild+ brass1 copp]1 & silv] is n v mat]ial4 ,ab\t "o to two p\nds ( gold potassium cyanide 78 #if p] c5t ,,kcn7 p] gallon does v well4 ,! gold is be/ introduc$ by electrolys+ f a l>ge to a small gold electrode4 ,"o pur*ases a plate ( pure gold ei!r f ! m9t or f reliable metallurgi/s 7say ,messrs4 ,johnson & ,mat!y ( ,london71 & f ?is electrodes are cut4 ,! relative areas ( ! electrodes d n really mu* matt]4 ,i h us$ an anode ( f\r times ! area ( ! ca?ode4 ,! solution is pref]ably heat$ to a temp]ature ( ab\t #ej ,c1 & a /rong curr5t is s5t ?r\gh x1 say tw5ty amp]es to ! squ>e foot ( anode4 ,! electrodes mu/ be susp5d$ bel[ ! surface ( ! solution by means ( plat9um wires4 ,if ! gold plates are only p>tly imm]s$1 !y dissolve mu* m rapidly :]e !y cut ! surface1 possibly on acc\nt ( ! effect ( convection curr5ts1 ?\gh s f> z ! writ] is aw>e no prop] explanation has yet be5 giv54 ,aft] a "t gold beg9s to be deposit$ on ! ca?ode 9 a p[d]y =m1 = :i* reason x is a good plan to beg9 by wrapp+ ! latt] 9 filt] pap]4 ,! process has gone on = a suffici5t "t :5 a clean bit ( plat9um foil imm]s$ 9 ! place ( ! ca?ode becomes prop]ly gilt at a curr5t d5sity ( ab\t t5 amp]es p] squ>e foot4 ,! p[d]y gold deposit$ on ! ca?ode :ile prep>+ ! solution c be scrap$ (f & melt$ = fur!r use1 or ! :ole ca?ode may n[ be us$ z an anode4 ,! plat9um foil te/+ ca?ode may also be /ripp$ by mak+ x an anode1 & is = ?is reason pref]able to ,g]man silv] or copp]1 :i* w\ld contam9ate ! solution :ile ! /ripp+ process 0 9 progress4 ,= g5]al purposes a curr5t d5sity ( say t5 to fifte5 amp]es p] squ>e foot may be us$1 b ?is may be consid]ably v>i$1 s long z ! upp] limit is n greatly ov]pass$4 ,dur+ gold-plat+ !re is a consid]able advantage 9 keep+ ! electrodes mov+ or ! solution /irr$4 ,aft] imm]s+ ! clean$ & scrat*-bru%$ articles1 deposit+ may g on = ab\t ?ree m9utes1 aft] :i* !y are remov$ f ! ba? & exam9$1 9 ord] to detect any want ( uni=mity 9 ! deposit4 ,! articles %\ld be entirely imm]s$2 if ?is is n done1 irregul>ity is apt to appe> at ! surface4 ,plat9um wires employ$ z susp5d]s1 & coat$ along ) ! articles to be gilt1 may also be clean$ )\t loss by mak+ !m anodes4 ,if1 on exam9ation1 all is f\nd to be go+ on well1 reimm]se ! ca?odes1 & cont9ue plat+ till !y appe> ( a dull yell[i% br[n 7?is w occur 9 ab\t f\r m9utes71 !n remove !m1 r9se & scrat*-bru% !m1 & replace !m 9 ! ba?4 ,:5 a second coat appe>s to be gett+ r br[n ?an yell[i% br[n1 i4e4 ( ! col\r ( wet wa%-lea!r1 ! removal1 foll[$ by scrat*-bru%+1 may be repeat$1 & = ne>ly all laboratory purposes1 ! articles are n[ fully gilt4 ,! coat+ ( gold deposit$ f a hot cyanide solution is spongy 9 ! extreme1 & if ! maximum we>-resi/+ effect is to be obta9$1 x is advisable to burni% ! gold r ?an to rely ^u ! scrat* bru% alone4 ,if ! area ( ! ca?ode exce$s t ( ! anode ! solution is said to gr[ weak]1 & vice v]sa4 ,?is may be rem$i$ 9 ! =m] case by an obvi\s readju/m5t2 ! latt] introduces no difficulty s f> z ,i "k except :5 plat+ iron or /eel4 ,! /ud5t ne$ n be tr\bl$ at ! poor appe>ance ( ! deposit be=e x is scrat*-bru%$4 ,heavy gold deposits are almo/ always dull1 n to say dirty1 9 appe>ance till ! burni%] or scrat* bru% is appli$4 ,on ! o!r h&1 ! deposit ought n to get any?+ l black 9 col\r4 ,! foll[+ indications ( defects may be not$--!y are tak5 f ,gore4 ,i h nev] be5 really tr\bl$ ) !m4 ,! deposit is blacki%4 ,?is is caus$ by too /rong a curr5t 9 too weak a ba?4 ,?is may be rem$i$ to "s ext5t by /irr+ or keep+ ! ca?ode 9 motion4 ,! obvi\s rem$y is to add a little cyanide ( gold4 ,! gold anode gets incru/$4 ,?is is a sign t ! ba? is defici5t 9 potassium cyanide4 ,! gold anode gets black & gives (f gas4 ,! solution is defici5t 9 cyanide1 & too l>ge a curr5t is be+ pass$4 ,if a bright surface is desir$ direct f ! ba?1 "s cau/ic pota% 7say #b p] c5t7 may1 accord+ to ,gore1 be add$1 or ! articles may be plat$ only slightly by us+ a weak curr5t & tak+ !m out directly !y %[ signs ( gett+ dull4 ,by a weak curr5t ,i mean "o ( ab\t five amp]es p] squ>e foot4 ,! deposit is said to be d5s] if ! solution be heat$ z direct$2 b ! ba? w gild1 ?\gh n q s freely :5 cold4 ,to gild iron or /eel directly1 dilute ! ba? z above recomm5d$ "s five or six times1 add ab\t #a p] c5t ( potassium cyanide1 & gild ) a v weak curr5t 7say two or ?ree amp]es p] squ>e foot7 9 ! cold4 ,frequ5t scrat*-bru%+ w be f\nd requisite to secure prop] adh]5ce4 ,x is g5]ally recomm5d$ to gild brass or ,g]man silv] 9 solutions :i* are r weak1 b 9 ! small practice :i* occurs 9 ! laboratory a solution prep>$ z sugge/$ does p]fectly = ev]y?+ except iron or /eel4 ,! scrat*-bru%+ %\ld be done ov] a l>ge photographic develop+ di% to avoid loss ( gold4 ,x is a good plan to r9se ! articles aft] leav+ ! ba? 9 a limit$ quantity ( di/ill$ wat]1 :i* is aft]w>ds plac$ 9 a residue bottle1 & !n to scrat*-bru% !m by h& ov] ! di% to cat* f9e gold4 ,:5 any loose du/ is remov$ ! articles may be scrat*$ 9 ! la! )\t appreciable fur!r loss4 ,silv]-gilt articles t5d to get discol\r$ by use1 b ?is discoloration c be remov$ by soap & wat]4 ,aft] long use a gold cyanide ba? t5ds to alt] greatly 9 composition1 ,9 g5]al1 ! ba? t5ds to gr[ weak]1 f ! fact t !re is a /rong temptation to gild z _m articles at once z possible4 ,x is !re=e a good plan to keep a r\gh pr(it & loss acc\nt ( ! gold 9 ord] to f9d ! quantity 9 solution4 ,fifty dwts4 p] gallon 7or #gh grms4 p] #d4e litres7 is recomm5d$4 ,a gallon ( solution ( ?is /r5g? is wor? ab\t elev5 p\nds /]l+ 9 gold & cyanide1 & a s]viceable anode w be wor? ab\t #aj p\nds4 7,f9e gold is wor? nom9ally f\r p\nds f\r %ill+s & elev5 p5ce ha'p5ny p] oz47 ,gold may be easily obta9$ conta9+ less impurity ?an "o "p 9 t5 ?\s&4 #acg4 ,plat+ ) ,copp]4 ,copp] may be deposit$ f almo/ any ( its salts 9 regul9e =m1 ! sulphate & nitrate be+ mo/ usually employ$4 ,9 ! laboratory a ne>ly saturat$ solution ( sulphate ( copp] ) #a or #b p] c5t ( sulphuric acid w answ] mo/ purposes4 ,a curr5t d5sity (1 at mo/1 fifte5 amp]es p] squ>e foot may be us$1 ei!r = obta9+ solid deposits = con/ructional purposes or = calibrat+ curr5t measur+ in/rum5ts by electrolysis4 ,a copp] anode is ( c\rse employ$4 ,:5 copp]+ ) a view to obta9+ ?ick deposits x is a good plan to place ! electrodes sev]al in*es ap>t1 &1 if possible1 to keep ! liquid /irr$1 z !re is a consid]able t5d5cy on ! "p ( copp] deposits to gr[ out into mossy masses :]ev] ! curr5t d5sity exce$s ! limit m5tion$4 ,z ! masses gr[ t[>ds ! anode ! defect naturally t5ds to increase ( itself1 h5ce ! necessity = c>e4 ,! ph5om5on is p>ticul>ly m>k$ at ! edges & corn]s ( ! ca?ode4 ,if ! deposit becomes m>k$ly irregul>1 ! be/ plan is to /op ! process & file ! face ( ! deposit d[n to approximate smoo?ness4 ,9 copp]+ x is ( ! utmo/ importance t ! ca?ode be clean & free f grease2 x mu/ nev] be t\*$ 7by ! f+]1 = in/ance7 f ! "t x is scrat*-bru%$ till x is imm]s$ 9 ! plat+ ba?4 ,any grease or oxidation t5ds to prev5t ! copp] deposit adh]+ prop]ly4 ,a copp] deposit oxidises v easily :5 expos$ to ! air4 ,consequ5tly if ! surface be requir$ free f oxide1 z1 = in/ance1 :5 x is to be silv]$ or gilt1 x mu/ be quickly wa%$ :5 )drawn f ! copp]+ ba?1 scrat*-bru%$1 & transf]r$ imm$iately to ! silv]+ or gild+ ba?4 ,if ! surface is to be dri$1 z 9 electrolysis calibrations1 x mu/ be r9s$ quickly ) boil+ wat] & press$ betwe5 %eets ( filt] pap]4 ,ano!r me?od :i* has be5 recomm5d$ is to r9se ! copp] 9--wat] slightly acidulat$ ) sulphuric acid 7:i* prev5ts oxidation71 !n 9 di/ill$ wat]1 & to dry by blott+ pap] & 9 front ( a fire1 tak+ c>e n to make ! plate too hot4 ,! wa% wat] is suffici5tly acidulat$ by ! addition ( two or ?ree drops ( acid p] litre4 ,s f> z ,i "k1 ! me?od ( wa%+ 9 acidulat$ wat] 0 fir/ propos$ by ,mr4 ,t4 ,gray4 #ach4 ,copp]+ ,alum9ium4 ,a good adh]5t deposit ( copp] on alum9ium us$ to be consid]$ a desid]atum 9 ! days :5 x af=d$ ! only means ( sold]+ ! latt]4 ,_m receipts h be5 publi%$ f "t to "t1 & ,i h tri$1 ,i ?9k1 mo/ ( !m4 ,on no occasion1 h[ev]1 till ?is ye> 7#ahif71 h ,i succe$$ 9 obta9+ a deposit :i* w\ld n /rip aft] x 0 t9n$ & sold]$1 ?\gh x is n difficult to get app>5tly adh]5t deposits s long z !y are n op]at$ ^u by ! sold]+ iron4 ,! be/ ( ! _m solutions :i* h be5 propos$ 9 ye>s gone by is v dilute cupric nitrate ) ab\t #e p] c5t ( free nitric acid4 ,! problem ( electroplat+ alum9ium :i* ,i h indicat$ z await+ a solution has at la/ f\nd "o4 ,9 ! ,ar*ives des ,sci5ces physiques et naturelles de ,g5ve = ,decemb] #ahie 7vol4 xxxiv4 p4 #efc7 !re is a pap] by ,m4 ,m>got on ! subject1 :i* discloses a p]fectly successful me?od ( plat+ alum9ium ) copp]4 ,! pap] itself deals 9 an int]e/+ way ) ! !ory ( ! matt]--h[ev]1 ! result is z foll[s4 7#a7 ,! alum9ium articles are boil$ = a few m9utes 9 a /rong solution ( ord9>y wa%+ soda4 ,! alum9ium surface is ?us corrod$ some:at1 & r5d]$ fav\rable to ! deposit ( an adh]5t film ( copp]4 ,aft] removal f ! soda solution ! alum9ium is well wa%$ & bru%$ 9 runn+ wat]4 7#b7 ,! articles are dipp$ = ?irty seconds or s 9 a hot #e p] c5t solution ( pure hydro*loric acid4 7#c7 ,aft] dipp+ 9 ! hydro*loric acid1 ! "w is in/antly plung$ into clean wat] = ab\t "o second1 s z to remove ne>ly1 b n q1 all ( ! alum9ium *loride4 7#d7 ,! "w is transf]r$ to a cold dilute 7say #e p] c5t7 solution ( cupric sulphate slightly acidulat$ ) sulphuric acid4 ,! degree ( acidulation does n appe> to be v important1 b ab\t "o-t5? p] c5t ( /rong acid does well4 ,if ! prelim9>y processes h be5 prop]ly c>ri$ out ! alum9ium w become coat$ ) copp]1 & ! process is accompani$ by ! dis5gagem5t ( gas4 ,x appe>s to be a rule t if gas is n giv5 (f1 ! film ( copp] deposit$ is non-adh]5t4 ,! "w mu/ be left 9 ! copp] sulphate solution till x has receiv$ a uni=m coat+ ( copp]4 7#e7 ,:5 ?is is ! case ! "w is remov$--well wa%$ s z to get rid ( ! re/ ( ! alum9ium *loride1 & !n electroplat$ by ! batt]y 9 ! ord9>y copp] sulphate ba?4 ,if ! op]ation 7#d7 does n appe> to give a uni=m coat1 or if gas is n evolv$ f e "p ( ! alum9ium surface1 ,i f9d t op]ations 7#b7 & 7#c7 may be repeat$ )\t dang]1 provid$ t ! dip 9 ! hydro*loric acid is %ort5$ to two or ?ree seconds4 ,! copp] lay] obta9$ by ,m>got's me?od is p]fectly adh]5t--ev5 :5 us$ z a base = ord9>y sold]--?\gh 9 ?is case x c be /ripp$ if suffici5t =ce is appli$4 ,s9ce ! sold] recomm5d$ by ,m4 ,m>got = alum9ium conta9s z9c1 x does n run well :5 us$ to unite alum9ium to copp]1 brass1 iron1 etc4 ,9 ?is case1 !re=e1 ,i h f\nd ! mo/ advantage\s me?od ( sold]+ to be by way ( a prelim9>y copp]-plat+4 ,! success ( ,m4 ,m>got's me?od dep5ds 9 my exp]i5ce on obta9+ j ! prop] am\nt ( alum9ium *loride 9 contact ) ! alum9ium :5 ! latt] is imm]s$ 9 ! copp] sulphate solution4 #aci4 ,! process ( copp]-plat+ f sulphate or nitrate may1 accord+ to ,mr4 ,swan 7,j\rnal ( ! ,royal ,in/itution1 #ahib1 p4 #fcj71 be consid]ably accel]at$ by ! addition ( a trace ( gelat9e to ! solution4 ,z success appe>s to dep5d ^u hitt+ ! exact p]c5tage am\nt ( ! gelat9e1 :i* mu/ 9 any case be b a fraction ( "o p] c5t1 & z ,mr4 ,swan refra9s f /at+ :at ! am\nt is1 ,i am unable to give m precise in/ructions4 ,a few exp]im5ts made on ! subject fail$1 d\btless ?r\gh ! gelat9e cont5t n hav+ be5 rightly adju/$4 ,mr4 ,swan claims to be able to get a h>d deposit ( copp] ) a curr5t d5sity ( #ajjj amp]es p] squ>e foot1 b seems to recomm5d ab\t "o-t5? ( t am\nt = g5]al use4 ,! solution employ$ is a mixture ( nitrate ( copp] & ammonium *loride--proportions n /at$4 ,electrolytic copp]1 z g5]ally prep>$1 is v pure1 b ?is is a m]e accid5t dep5d+ on ! impurities :i*1 z a rule1 h to be got rid (4 ,electrolysis seems to h no effect 9 purify+ f ars5ic1 = in/ance4 ,r\ghly speak+1 ab\t #aa grms4 ( copp] are deposit$ p] amp]e h\r f cupric salt solutions4 ,:5 ! curr5t d5sity is too high ! anode suff]s by oxidation1 & ?is introduces a l>ge & v v>iable resi/ance into ! circuit4 #adj4 ,alkal9e ,copp]+ ,solution ,copp]+ ,base ,metals4 ,x is (t5 desirable to coat lead1 z9c1 pewt]1 iron1 etc1 ) a firm & uni=m lay] ( copp] prep>atory to gild+ or silv]+4 ,if copp] or brass articles are sold]$ ) s(t sold] x is f\nd t ! sold] does n become silv]$ or gilt along ) ! re/ ( ! mat]ial1 b rema9s uncoat$ & ( an ugly d>k col\r4 ,?is defect is got ov] by giv+ a prelim9>y coat+ ( copp]4 ,?is is done 9 an alkal9e solution1 g5]ally conta9+ cyanog5 & ammonia4 ,! foll[+ me?od has succe$$ rem>kably well ) me4 ,! receipt 0 tak5 orig9ally f ,gore's ,electro-metallurgy1 p4 #bjh4 ,a solution is made ( #ej grms4 ( potassium cyanide 7ord9>y comm]cial1 say1 #ge p] c5t7 & #cj grms4 ( sodium bisulphite 9 ,i4#e litres ( wat]4 ,?irty-five grammes ( cupric acetate are dissolv$ 9 a litre ( wat]1 & #bj cubic c5timetres ( ! /ronge/ liquid ammonia are add$4 ,! precipitate =m$ mu/ be m or less dissolv$ to a /rong blue solution4 ,! cyanide & bisulphite solution is !n add$ ) w>m+ till ! blue col\r is de/roy$4 ,?is usually requires ! exact am\nt ( cyanide & bisulphite m5tion$1 b ,i h n f\nd x ess5tial to entirely de/roy ! col\r4 ,! solution conta9s cuprocyanide ( sodium & ammonium 7871 :i* is n v soluble1 & ?is salt t5ds to be deposit$ 9 granul> cry/all9e masses on /&+4 ,h[ev]1 at a temp]ature ( #ej ,c4 ! above receipt gives an excell5t copp]+ liquid1 :i* w coat z9c ) a f9e regul9e deposit4 ,brass or copp] p>tly sme>$ ) sold] w receive a deposit ( copp] on ! latt] z well z on ! =m]1 &1 moreov]1 a deposit :i* appe>s to be p]fectly uni=m4 ,9 us+ ! ba? ! anode t5ds1 z a rule1 to become incru/$1 & ?is rapidly increases ! resi/ance ( ! cell1 s t ! curr5t falls (f quickly4 ,! articles %\ld be scrat*-bru%$ & plat$ = ab\t two m9utes ) a curr5t d5sity ( ab\t t5 ampres p] squ>e foot4 ,z soon z ! deposit beg9s to look r$ ! articles are to be remov$ & rebru%$1 aft] :i* ! process may be cont9u$4 ,ab\t five m9utes' plat+ w give a copp] deposit q ?ick en\gh aft] scrat*-bru%+ to all[ ( a v ev5 gild+ or silv]+4 ,alum9ium appe>s to be fairly coat$1 b1 z usual1 ! copp] /rips aft] sold]+4 ,iron receives an excell5t & adh]5t coat4 ,i d n ?9k t ! =mation ( a cru/ ^u ! anode c be entirely prev5t$4 ,accord+ to ,gore1 its =mation is due to ! solution be+ too poor 9 copp]1 b ,i h add$ a solution ( ! acetate ( copp] & ammonium till ! col\r 0 bright blue )\t 9 any way r$uc+ ! incru/ation4 ,if ! solutions become viol5tly blue x is p]haps z well to add a little m cyanide & bisulphite1 b ,i h n f\nd su* an addition necess>y4 ,! process is "o ( ! easie/ & mo/ satisfactory 9 electro-metallurgy4 #ada4 ,nickel-plat+4 ,an exam9ation ( sev]al ,am]ican samples ( nickel-plat$ goods has disclos$ t ! coat+ ( nickel is1 z a rule1 exce$+ly ?94 ,?is is :at "o w\ld expect f laboratory repetition ( ! processes employ$4 ,comm]cial practice 9 ! matt] ( ! composition ( nickell+ solutions appe>s to v>y a good deal4 ,?9 coat+s ( nickel may be readily giv5 9 a solution ( ! d\ble sulphate ( nickel & ammonia1 :i* does r bett] if slightly alkal9e4 ,deposits f ?is solution1 h[ev]1 become gray if ( any ?ickness1 &1 moreov]1 are-apt to flake (f ! "w4 ,! foll[+ solution has giv5 v good results ) me4 ,x is m5tion$1 toge!r ) o!rs1 9 ! ,electrical ,review1 #g? ,june #ahie4 ,! +r$i5ts are3- ,nickel sulphate #e p>ts ,ammonia suffici5t to neutralise ! nickel salt4 ,ammonium t>trate #c4ge p>ts ,tann9 #j4jbe p>ts ,wat] #ajj p>ts ,! nickel sulphate & ammonia are dissolv$ 9 half ! wat]1 ! ammonium t>trate 9 ! o!r half ) ! tann94 ,! solutions are mix$ & filt]$ at ab\t #dj ,c4 ,?is solution works well at ord9>y temp]atures1 or slightly w>m1 ) a curr5t d5sity ( t5 ampres p] squ>e foot4 ,9 an exp]im5t made = ! purpose ,i f\nd t plat+ may g on = an h\r 9 ?is solution be=e ! deposit beg9s to %[ signs ( flak+ (f4 ,! deposit is ( a f9e :ite col\r4 ,! resi/ance ( ! ba? is r high & r v>iable1 consequ5tly x is z well to h a curr5t indicator 9 circuit1 & x may well happ5 t five or six volts w be f\nd requisite to get ! curr5t up to ! value /at$4 ,= nickell+ small objects ( brass1 su* z b9d+ screws1 etc1 x is v necess>y to be c>eful z to ! /ate ( poli% & uni=mity ( _! surfaces be=e plac+ !m 9 ! plat+ ba?4 ,a poli%$ surface w appe> :5 coat$ z a poli%$ surface1 & a mat surface z a mat surface2 moreov]1 any local irregul>ity1 su* z a speck ( a =eign metal1 w give rise to an ugly spot 9 ! nickell+ ba?4 ,= ?is reason x is (t5 advisable to comm5ce ) a coat ( copp] laid on 9 an alkal9e solution & scrat*-bru%$ to absolute uni=mity4 ,an exam9ation ( ! "w w1 h[ev]1 disclose :e!r su* a c\rse is desirable or n2 x is n done 9 ,am]ican practice1 at all ev5ts = small brass objects4 ,^! are clean$ 9 alkali & 9 boil+ cyanide1 :i* does n r5d] a poli%$ surface mat1 z weak acid is apt to d1 & are !n coat$ ) a curr5t d5sity ( ab\t t5 ampres p] squ>e foot4 ,9 spite ( :at is to be f\nd 9 books z to ! ease ) :i* nickel deposits may be poli%$1 ,i f9d t ! mat surface obta9$ by plat+ on an imp]fectly poli%$ ca?ode ( iron is by no means easily poli%$ ei!r by f9e em]y1 tripoli1 or r\ge4 ,consequ5tly1 z 9 ! case ( brass1 if a poli%$ surface is desir$1 x mu/ be fir/ prep>$ on ! unplat$ ca?ode4 ,9 ?is case1 ev5 if ! deposit appe>s dull1 b n gray1 x may be easily poli%$ by tripoli & wat]1 us+ a cork z ! poli%]4 ,scrat*-bru%+ ) brass wire1 h[ev]1 ?\gh possibly n ) ,g]man silv] wire1 bright5s ! deposit1 b discol\rs x4 ,:5 ! deposit becomes gray ,i h n succe$$ 9 poli%+ x satisfactorily4 ,sold]$ brass or iron may be satisfactorily coat$ ) nickel by giv+ x a prelim9>y coat+ ( copp] 9 ! cyanide ba?4 ,on ! :ole1 ,i recomm5d 9 g5]al t iron be fir/ coat$ ) copp] 9 ! alkal9e ba?1 scrat*-bru%$1 & !n nickel-plat$1 & ?is :e!r ! iron appe>s to be uni=m or n4 ,mu* smoo!r1 ?ick]1 & /rong] coats ( nickel are obta9$ ^u ! copp]-plat$ surface ?an on ! iron "o1 & ! coat+ does n become discol\r$ 78 by iron ru/7 9 ! same way t a coat+ on b>e iron does4 ,! copp] surface may be plat$ = at lea/ an h\r at a d5sity ( t5 ampres p] squ>e foot )\t scal+4 ,scales or circles divid$ on brass may be greatly improv$ 9 durability by nickel--plat+4 ,= ?is purpose ! brass mu/ be highly poli%$ & divid$ be=e x is nickell$4 ,! plat+ %\ld be cont9u$ = a few m9utes only1 :5 a v bright b ?9 coat ( nickel w be deposit$2 x !n only rema9s to wa% & dry ! "w1 & ?is mu/ be done at once4 ,if ! nickel is deposit$ be=e ! scale or circle is engrav$1 v f9e & legible divisions are obta9$1 b !re is a risk t flakes ( nickel may become deta*$ "h & !re 9 ! process ( engrav+4 #adb4 ,miscellane\s ,notes on ,electroplat+4 ,occasionally x is desirable to make a metallic m\ld or o!r object ( complex %ape4 ,! quicke/ way to d ?is is to c>ve ! object out ( h>d p>aff91 & !n copy x by electrotyp+4 ,electrotype m\lds c be made 9 _m ways4 ,! easie/ way p]haps is to take a ca/+ 9 pla/] ( ,p>is1 or by means ( pressure 9 w>m gutta-p]*a4 ,9 cases :]e ! m\ld w n draw1 rec\rse mu/ be _h to ! devices ( iron-f\nd]s1 i4e4 ! pla/] ca/ mu/ be made 9 suitable pieces1 & ^! aft]w>ds fitt$ toge!r4 ,?is process c occasionally be replac$ by ano!r 9 :i* ! m\ld+ mat]ial is a mixture ( treacle & glue4 ,! glue is soak$ 9 cold wat] till x is completely s(t4 ,! sup]flu\s wat] ?r[n away1 "o-f\r? "p by volume ( ?ick treacle is add$1 & ! mixture is melt$ on ! wat] ba?2 dur+ :i* process /irr+ has to be resort$ to1 to produce a uni=m mixture4 ,?is liquid =ms ! m\ld+ mixture1 & x is all[$ to fl[ r\nd ! object to be copi$1 conta9$ 9 a suitable box1 ^: sides h be5 slightly oil$4 ,! object to be copi$ %\ld also be oil$4 ,aft] "s h\rs1 :5 ! glue mixture has set1 x w be f\nd to be highly ela/ic1 s t x may be pull$ away f ! m\ld1 & aft]w>ds resume v ne>ly its orig9al =m4 ,"o drawback to ! use ( ^! m\lds lies 9 ! fact t ! gelat9e w r>ely /& ! plat+ solution )\t und]go+ *ange1 b ?is may be p>tially obviat$ by dipp+ x = a few seconds 9 a #aj p] c5t solution ( bi*romate ( pota%1 expos+ x to ! sunlight = a few m9utes1 & !n r9s+ x4 ,9 ord] to r5d] ! surface conduct+1 x is wa%$ ov] ) a solution ( a gold or silv] salt1 & ! latt] r$uc$ 9 situ to metal by a suitable reag5t4 ,a solution ( phosphorus is ! mo/ usual "o 7see ,gore1 ,electro-metallurgy1 p4 #baf74 ,su* a m\ld may be copp]-plat$ 9 ! sulphate ba?1 connection be+ made by wires suitably ?ru/ into ! mat]ial4 ,pla/] ( ,p>is m\lds require to be dri$ & wax$ by /&+ on a hot plate 9 melt$ wax be=e !y are imm]s$ 9 ! plat+ ba?4 ,9 ?is case ! surface is be/ made conduct+ ei!r by silv]+ x by ! silv]+ process us$ = mirrors1 or by bru%+ x ov] ) good black lead r5d]$ m conduct+ by moi/5+ ) an e!real solution ( *loride ( gold & !n dry+ 9 ! sun4 ,! bru%+ requires a /iff camel's-hair p5cil ( l>ge size cut s t ! hairs project to a di/ance ( ab\t a qu>t] ( an in* f ! hold]4 ,! bru%+ mu/ cont9ue till ! surface is bright1 & is (t5 a l5g?y process4 ,! same process ( blacklead+ may be employ$ to get a coat ( deposit$ metal :i* w /rip easily f ! ca?ode4 ,9 all cases :]e ext5sive deposits ( copp] are requir$1 ! gr[? takes place too rapidly at ! corn]s4 ,consequ5tly x is (t5 desirable to localise ! action ( ! deposit4 ,a /opp+ ( ord9>y copal v>ni% seems to be ! usual ?+1 b a ?9 coat ( wax or p>aff9 or photographic 7black7 v>ni% does practically z well4 ,i d n propose to deal ) ! subject ( electrotyp+ to any ext5t1 = if practis$ z an art1 a good _m little precautions are requir$1 z ! /ud5t may read 9 ,gore's ,electro-metallurgy4 ,! above in/ructions w be f\nd suffici5t = ! occasional use ( ! process 9 ! con/ruction ( app>atus1 etc4 ,!re is no advantage 9 attempt+ to hurry ! process1 a curr5t d5sity ( ab\t t5 ampres p] squ>e foot be+ q suitable & suffici5tly l[ to ensure a solid deposit4 #adc4 ,black+ ,brass ,surfaces4 ,a really uni=m dead-black surface is difficult to produce on brass by *emical means4 ,a pa/e ( nitrate ( copp] & nitrate ( silv] heat$ on ! brass is said to give a dead-black surface1 b ,i h n succe$$ 9 mak+ x act uni=mly4 ,= optical purposes ! be/ plan is to use a pa9t made up ( drop black1 gr\nd v f9e ) a little %ellac v>ni%1 & dilut$ = use ) alcohol4 ,no m v>ni% ?an is necess>y to cause ! black to hold toge!r %\ld be employ$4 ,9 g5]al1 if ! pa9t be gr\nd to ! consi/5cy ( v ?ick cream ) ord9>y %ellac v>ni% x w be f\nd to "w well :5 r$uc$ by alcohol to a free pa9t+ consi/5cy4 ,a v f9e gray & black f9i%1 ) a r metallic lu/re1 may be easily giv5 to brass "w4 ,= ?is purpose a dilute solution ( plat9um tetra*loride 7n /rong] ?an #a p] c5t7 is prep>$ by dissolv+ ! salt 9 di/ill$ wat]4 ,! poli%$ brass "w is clean$ by rubb+ ) a cork & /rong pota% till all grease has disappe>$1 z %[n by wat] /&+ uni=mly on ! metal & dra9+ away )\t ga!r+ into drops4 ,aft] copi\s wa%+ ! "w is :olly imm]s$ 9 a consid]able volume ( ! plat9um tetra*loride solution at ! ord9>y temp]ature4 ,aft] ab\t a qu>t] ( an h\r ! brass may be tak5 out & wa%$4 ,! surface w be f\nd to be nicely & uni=mly coat$ if ! above in/ructions h be5 c>ri$ out1 b any f+]-m>ks or o!rwise dirty places w cause irregul>ity ( deposit4 ,if ! process has be5 successful x w be f\nd t ! deposit adh]es p]fectly1 h>dly any ( x be+ remov$ by vigor\s rubb+ ) a clo?4 ,if ! deposit is all[$ to ?ick5--ei!r by leav+ ! articles 9 ! solution too long or heat+ ! solution1 or hav+ x too /rong--x w m]ely rub (f & leave an irregul> surface4 ,?is process succe$s well ) yell[ brass & ,muntz metal1 ei!r ca/ or roll$1 b x does n give q su* uni=m 7?\gh /ill good7 results ) gun-metal1 on :i*1 h[ev]1 ! deposit is d>k] & dead] 9 appe>ance4 ,a book might be writt5 7sev]al h be5 writt57 on ! art ( metal col\r+1 b ?\gh d\btless a beautiful & delicate art1 x is ( little s]vice 9 ! laboratory4 ,= fur!r in=mation ! read] may consult a "w by ,hiorns4 #add4 ,sieves4 ,prop]ly grad$ sieves ) me%es ( a reliable size are (t5 ( great use4 ,!y %\ld be made out ( prop] bolt+ clo?1 a beautiful mat]ial made = fl\r-mill]s4 ,messrs4 ,h5ry ,simon & ,company ( ,man*e/] h k9dly furni%$ me ) ! foll[+ table ( mat]ials us$ 9 fl\r-mill+4 ,sieves made ( ^! mat]ials w be f\nd to "w mu* m quickly & satisfactorily ?an ^? made f ord9>y musl9 or wire gauze4 ,relative ,bolt+ ,value ( ,silk1 ,wire1 & ,grit ,gauze ,?reads p] in* ,trade ,no4 ,trade ,no4 ,trade ,no4 ( ,approximate4 ( ,silk4 ( ,wire4 ,grit ,gauze4 #ah #jjjj #ah #af #bb #jjj #bj #bj #bh #jj #bf #bf #ch #j #cb #cd #dh #a #dj #dd #eb #b #de #ej #ef #c #ej #ed #fj #d #ef #eh #fd #e #fj #fj #gb #f #fd #ff #hj #g #gj #gj #hd #h #hj #hj #id #i #ajf #aj #aad #aa #abd #ab #acj #ac #aci #ad #adh #ae #aef #af #afc #ag #afg #ah #agj #ai #agc #bj #ade4 ,pott]y mak+ 9 ! ,laboratory4 ,:5 l>ge pieces ( e>!nw>e ( any special design are requir$1 rec\rse mu/ be _h to a pott]y4 ,small vessels1 plates1 p>ts ( ma*9es1 etc1 c (t5 be made 9 ! laboratory 9 less "t ?an x w\ld take to expla9 to ! pott] :at is requir$4 ,= ?is purpose any good pipeclay may be employ$4 ,i h us$ a :ite pipe-clay dug up 9 ! laboratory g>d5 ) complete success4 ,! clay %\ld be knead$ ) wat] & squeez$ ?r\gh a clo? to sep>ate grit4 ,x is !n mix$ ) its own volume or !reab\ts ( p[d]$ porcela9 evaporat+ bas9s1 brok5 bas9s be+ kept = ?is purpose4 ,! smoo?ness ( ! result+ e>!nw>e w dep5d on ! f95ess to :i* ! porcela9 fragm5ts h be5 r$uc$4 ,i h f\nd t fragm5ts pass+ a sieve ( sixty ?reads to ! in* run1 d v well1 ?\gh ! result+ e>!nw>e is decid$ly r\gh4 ,! porcela9 & clay be+ ?or\ghly incorporat$ by knead+1 ! articles are m\ld$1 x be+ borne 9 m9d t !y w contract some:at on fir+4 ,footnote3 ,! contraction dep5ds on ! temp]ature atta9$ z well z on ! "t4 ,an all[ance ( "o "p 9 twelve w be suitable 9 ! case consid]$4 ,! clay %\ld be z /iff z is conv5i5t to "w1 & aft] m\ld+ mu/ be all[$ to get ?or\ghly dry by /&+ 9 an airy place2 ! dry+ mu/ n be =c$1 especially at fir/1 or ! clay w crack4 ,small articles are readily fir$ 9 a ,flet*]'s crucible furnace suppli$ ) a gas bl[-pipe2 ! furnace is heat$ gradually to beg9 )4 ,:5 a dull r$ heat is atta9$1 ! full p[] ( ! bla/ may be turn$ on1 & ! furnace kept at its maximum temp]ature = ?ree or f\r h\rs at lea/1 ?\gh on an em]g5cy %ort] p]iods may be made to d4 ,! articles are support$ on a b$ ( :ite s&2 aft] fir+1 ! crucible furnace mu/ be all[$ to cool sl[ly4 ,x mu/ be rememb]$ t ! furnace walls w get hot ext]nally aft] ! fir/ few h\rs1 consequ5tly ! furnace mu/ be support$ on bricks1 to protect ! b5*4 ,! pott]y :5 cold may be dress$ on a gr9d/one if necess>y4 ,?is amateur pott]y w be f\nd ( s]vice 9 mak+ small fitt+s = swit*-bo>ds1 commutators1 & 9 electrical "w g5]ally4 ,pott]y made z describ$ is v h>d & /rong1 ! h>dness & /r5g? dep5d+ 9 a great degree on ! proportion ( p[d]$ porcela9 add$ to ! clay1 z well1 ( c\rse1 z on ! quality ( bo? ( ^! mat]ials4 ,x is a good plan to knead a consid]able quantity ( ! mixture1 :i* may !n be plac$ 9 a well-cov]$ j>1 & kept damp by ! addition ( a little wat]4 ,pott]y ?us made does n require to be glaz$1 b1 ( c\rse1 a glaze c be obta9$ by any ( ! me?ods describ$ 9 works on pott]y manufacture4 ,! foll[+ glaze has be5 recomm5d$ to me by a v compet5t pott]3- ,li?>ge #g p>ts by weight ,gr\nd fl9t #b p>ts by weight ,corni% /one or felsp> #a p>ts by weight ,^! +r$i5ts are to be gr\nd up till !y w pass ! f9e/ sieve--say #ahj ?reads to ! in*4 ,!y are !n mix$ ) wat] till !y =m a pa/e ( ! consi/5cy ( cream4 ,!y mu/1 ( c\rse1 be mix$ toge!r p]fectly4 ,! w>e to be glaz$ is dipp$ into ! cream aft] ! fir/ fir+2 x is !n dri$ z be=e & refir$4 ,! glaze w melt at a bright r$ heat1 b x w crack if n fir$ h>d]2 ! h>d] x is fir$ ! less likely is x to crack4 ,if col\r+ matt]s are add$ !y mu/ be gr\nd 9 a mill free f iron till !y are s f9e t a ?ick blanket filt] w n filt] !m :5 susp5d$ 9 wat]4 ,?is rem>k applies p>ticul>ly to oxide ( cobalt4 ,,app5dix ,,plat9is+ ,,glass ,,9 ! ,philosophical ,magaz9e = ,july #ahhh 7vol4 xxvi4 p4 #a7 !re is a pap] by ,pr(essor ,kundt translat$ f ! ,sitzungsb]i*te ( ! ,prussian ,academy4 ,?is pap] deals ) ! indices ( refraction ( metals4 ,?9 prisms 7 obta9$ by deposit+ metals electrolytically on glass surfaces coat$ ) plat9um4 ,! prep>ation ( ^! surfaces is tr\blesome4 ,kundt rec\nts t no less ?an two ?\s& trials 7 made be=e success 0 atta9$4 ,a detail$ acc\nt ( ! prep>ation ( ^! surfaces is n giv5 by ,kundt1 b "o is promis$--a promise un=tunately unfulfill$ s f> z ,i am able to discov]4 ,a hunt ?r\gh ! lit]ature l$ to ! discov]y ( ! foll[+ ref]5ces3 ,c5tral ,zeitung fu] ,optik und ,me*anik1 p4 #adb 7#ahhh72 ,d+l]'s ,polyte*nik ,j\rnal1 ,vol4 cxcv4 p4 #dfd2 ,comptes ,r5dus1 vol4 lxx4 7#ahgj74 ,! orig9al communication is a pap] by ,j\glet 9 ! ,comptes ,r5dus1 ( :i* ! o!r ref]5ces are ab/racts4 ,! acc\nt 9 ,d+i] is a lit]al translation ( ! orig9al pap]1 & ! note 9 ! ,c5tral ,zeitung is abbreviat$ suffici5tly to be ( no value4 ,! details are briefly z foll[s3- ,"o hundr$ grams ( plat9um are dissolv$ 9 aqua regia & ! solution is dri$ on ! s& ba?1 )\t1 h[ev]1 produc+ decomposition4 ,?\gh ! in/ructions are n def9ite1 ,i presume t ! =mation ( ,pt,cl#d is contemplat$4 ,! dri$ salt is add$ little by little to rectifi$ oil ( lav5d]1 plac$ on a glass pa9t-gr9d+ plate1 & ! salt & oil are gr\nd toge!r ) a mull]4 ,c>e is requir$ to prev5t any appreciable rise ( temp]ature :i* w\ld decompose ! comp\nd aim$ at1 & x is = ?is reason t ! salt is to be add$ gradually4 ,( c\rse ! absorption ( wat] f ! air mu/ be prev5t$ f tak+ place z f> z possible4 ,f9ally1 ! comp\nd is dilut$ by add+ oil ( lav5d] up to a total weight ( #adjj grams 7( oil74 ,! liquid is p\r$ into a porcela9 di% & left absolutely at re/ = eight days4 ,x is !n decant$ & filt]$1 left six days at re/1 & aga9 decant$ 7if necess>y74 ,! liquid %\ld h a specific gravity ( #e on ! acid hydromet]4 7,if by ?is ! ,baum scale is int5d$1 ! correspond+ specific gravity w\ld be #a4jcg47 ,a second liquid is prep>$ by gr9d+ up #be grams ( li?>ge ) #be grams ( borate ( lead & #h to #aj grams ( oil ( lav5d]4 ,! gr9d+ mu/ be ?or\ghly c>ri$ out4 ,?is liquid is to be add$ to ! "o fir/ describ$1 & ! :ole well mix$4 ,! result+ fluid con/itutes ! plat9is+ liquid1 & is appli$ z foll[s3- ,a %eet ( clean glass is held v]tically1 & ! liquid is pa9t$ ov] x1 c>ry+ ! bru% f ! l[] to ! upp] edge4 ,! lay] ( oil dries sl[ly1 & :5 x is dry ! pa9t+ is aga9 proce$$ )1 mov+ ! bru% ?is "t f "r to left2 & simil>ly ! process is repeat$ twice1 ! bru% be+ c>ri$ f top to bottom & left to "r4 ,?is is ) ! object ( secur+ great uni=mity 9 ! coat+4 ,no?+ is said z to ! mann] 9 :i* ! glass is to be dri$4 ,! dri$ glass is f9ally heat$ to a temp]ature ( dull r$ness 9 a muffle furnace4 ,! res9\s lay] burns away )\t runn+ or bubbl+1 & leaves a dull metallic surface4 ,z ! temp]ature rises ?is sudd5ly bright5s1 & we obta9 ! desir$ surface 7:i* probably consi/s ( an alloy ( lead & plat9um74 ,x is bright only on ! surface away f ! glass4 ,i h n _h an opportunity ( try+ ?is process s9ce ,i discov]$ ! detail$ acc\nt giv5 by ,j\glet2 b _m modifications h be5 tri$ 9 ! laboratory ( ! ,sydney ,univ]sity by ,mr4 ,pollock1 />t+ f ! imp]fect note 9 ! ,c5tral ,zeitung1 :i* l$ to no real success4 ,x 0 f\nd t x is p]fectly easy to obta9 brilliant films ( plat9um by ! foll[+ process1 provid$ t ! pres5ce ( a few p9-holes does n matt]4 ,! plat9um salt employ$ is :at is b\ght "u ! "n ( plat9ic *loride2 x is1 h[ev]1 probably a mixture ( ?is salt & hydro-*loro-plat9ic acid1 & has all ! appe>ance ( hav+ be5 obta9$ by evaporat+ a solution ( plat9um 9 aqua regia to dryness on ! wat] ba?4 ,a solution ( ?is salt 9 di/ill$ wat] is prep>$2 ! /r5g? does n seem to matt] v mu*1 b p]haps "o ( salt to n9ety-n9e wat] may be reg>d$ z a /&>d proportion4 ,to ?is solution is add$ a few drops ( ord9>y gum wat] 7i4e4 a solution ( dextr974 ,! exact quantity does n matt]1 b p]haps ab\t #b p] c5t may be m5tion$ z giv+ good results4 ,! glass is pa9t$ ov] ) ?is solution & dri$ sl[ly on ! wat] ba?4 ,:5 ! glass is dry1 & cov]$ ) a uni=m h>d film ( gum & plat9um salt free f bubble holes1 x is heat$ to r$ness 9 a muffle furnace4 ,! necess>y & suffici5t temp]ature is rea*$ z soon z ! glass is j s5sibly r$-hot4 ,! mirrors obta9$ 9 ?is way are v brilliant on ! free plat9um surface4 ,if ! gum be omitt$1 ! plat9um w h a mat surface2 & if too mu* gum be us$1 ! plat9um w get spotty by bubbles bur/+4 ,!re does n appe> to be any advantage 9 us+ lead4 ,x is q ess5tial t ! film be dry & h>d be=e ! glass is fir$4